Hey OSA,
I got another one to bring you today. This is by far the longest write-up I've done yet. This will be a total of 6 posts and 30 pictures. Fair warning!
This watch was an absolute honor to work on. It is an OSA member owned watch which he received while in Vietnam. I will not call him out by name, but he is more than welcome to let the group know who's watch this is if he chooses to do so.
This is a Benrus military issue Pilot's watch, manufactured in July of 1971.
A little history on this one first. Since the Vietnam war, they had issued military watches, made under GG-W-113 specification, to their pilots. These watches were manufactured under government contract by various American watch companies such as Benrus, Hamilton, and Waltham. The GG-W-113 watches had striking resemblances to military field watches (made under MIL-W-46374 specification) that were issued to soldiers on the ground. Same case, same hands were used, along with the usual 24 hour markings on a black dial. Both GG-W-113 and MIL-W-46374 watches were equipped with manual-wind movements. The GG-W-113 watches, however, differed in the following aspects (data pulled from a website):
1. Equipped with a 17 jewel manual-wind movement, it had the desirable hack feature, allowing precise synchronization of watches to a known source of time. MIL-W-46374 did not have the hack feature until the mid-eighties.
2. H3 and propeller shaped radiation marks were omitted from the dial to make the dials more legible.
3. Watches were normally issued with black (instead of olive drab) nylon band, although some were issued with olive drab band in Vietnam.
When I first learned that this model was specifically a pilot's watch, I pm'd the OSA member and asked if he was a pilot during his time in Vietnam. In his reply he told me a bit about his service history. One part of his response, telling me how he came into the watch, made me chuckle: “I acquired the watch mid or late 1972 from a crusty old lifer Army supply sergeant. …..old supply sergeants are known to be scroungers so there is no telling how he came to have them but he had three and with me needing a watch that I wouldn't have to baby I gave him a few dollars, signed a fictitious name to get it off his books and wore it daily till I returned from VN.”
The watch looked to be in really great shape when I received it. The OSA member had mentioned to me that he was planning on giving it to his son, and would like to make sure that it is in good running order. He initially thought that the watch had never been worked on, but we found out later that wasn't the case (will explain later on). During the initial inspection while testing the basic functions (before doing any disassembly), everything appeared to work except the hacking feature. While doing my research on this watch, everything I read pointed me to this watch having a hacking seconds feature, but it just wouldn't work. I spoke with the OSA owner of this watch, and he told me that he never remembered it having the seconds hand stop when the crown was pulled out to set the time. After the initial inspection, and him agreeing to let me do a complete overhaul, he told me that if it was there, and was fixable, to go ahead and get it working, but it had never worked to his memory so it wasn't a big deal if the hack didn't function. The crystal looked to be in good shape when I first received it. Once put under magnification I found several smaller scratches. These aren't even noticeable when you're wearing/looking at the watch, but now that I saw them they needed to be addressed!
Since the watch would run when it was first received, before doing any work it I put a full wind in the watch, and put it on the timegrapher to get some base-line readings.
You can see from these readings that the watch in the dial up position is running quite slow at 71 seconds per day. It had very low amplitude (degree of rotation of the balance wheel in each direction) of 184 degrees. This is considered very low on a full wind for a movement of this type. The amplitude gives you an idea of how efficiently power is transferring from the mainspring, through the mechanics of the watch and into the balance. The less power getting to the balance, the lower the amplitude you'll have (also must take into account the pivots on the balance itself – which are critical). It had a beat error of 2.8 milliseconds. The beat error is the difference in time between the clockwise swing and the counterclockwise swing of the balance. That isn't really all that bad for a vintage watch, and would be considered acceptable in some standards. If the watch was keeping good time, but still had a beat error of 2.8m/s, many watchmaker's wouldn't even bother with it. I suppose my OCD is a good thing when it comes to watchmaking. I knew that if it was 2.8 to start out before any service work that I could get it closer to 0 m/s, which is the ideal. Technically speaking, anything at 1.0 m/s or lower would make no difference in the watches ability to keep time accurately.
Here's a few pics of the initial tear down:
Continued on next post.
I got another one to bring you today. This is by far the longest write-up I've done yet. This will be a total of 6 posts and 30 pictures. Fair warning!
This watch was an absolute honor to work on. It is an OSA member owned watch which he received while in Vietnam. I will not call him out by name, but he is more than welcome to let the group know who's watch this is if he chooses to do so.
This is a Benrus military issue Pilot's watch, manufactured in July of 1971.
A little history on this one first. Since the Vietnam war, they had issued military watches, made under GG-W-113 specification, to their pilots. These watches were manufactured under government contract by various American watch companies such as Benrus, Hamilton, and Waltham. The GG-W-113 watches had striking resemblances to military field watches (made under MIL-W-46374 specification) that were issued to soldiers on the ground. Same case, same hands were used, along with the usual 24 hour markings on a black dial. Both GG-W-113 and MIL-W-46374 watches were equipped with manual-wind movements. The GG-W-113 watches, however, differed in the following aspects (data pulled from a website):
1. Equipped with a 17 jewel manual-wind movement, it had the desirable hack feature, allowing precise synchronization of watches to a known source of time. MIL-W-46374 did not have the hack feature until the mid-eighties.
2. H3 and propeller shaped radiation marks were omitted from the dial to make the dials more legible.
3. Watches were normally issued with black (instead of olive drab) nylon band, although some were issued with olive drab band in Vietnam.
When I first learned that this model was specifically a pilot's watch, I pm'd the OSA member and asked if he was a pilot during his time in Vietnam. In his reply he told me a bit about his service history. One part of his response, telling me how he came into the watch, made me chuckle: “I acquired the watch mid or late 1972 from a crusty old lifer Army supply sergeant. …..old supply sergeants are known to be scroungers so there is no telling how he came to have them but he had three and with me needing a watch that I wouldn't have to baby I gave him a few dollars, signed a fictitious name to get it off his books and wore it daily till I returned from VN.”
The watch looked to be in really great shape when I received it. The OSA member had mentioned to me that he was planning on giving it to his son, and would like to make sure that it is in good running order. He initially thought that the watch had never been worked on, but we found out later that wasn't the case (will explain later on). During the initial inspection while testing the basic functions (before doing any disassembly), everything appeared to work except the hacking feature. While doing my research on this watch, everything I read pointed me to this watch having a hacking seconds feature, but it just wouldn't work. I spoke with the OSA owner of this watch, and he told me that he never remembered it having the seconds hand stop when the crown was pulled out to set the time. After the initial inspection, and him agreeing to let me do a complete overhaul, he told me that if it was there, and was fixable, to go ahead and get it working, but it had never worked to his memory so it wasn't a big deal if the hack didn't function. The crystal looked to be in good shape when I first received it. Once put under magnification I found several smaller scratches. These aren't even noticeable when you're wearing/looking at the watch, but now that I saw them they needed to be addressed!
Since the watch would run when it was first received, before doing any work it I put a full wind in the watch, and put it on the timegrapher to get some base-line readings.
You can see from these readings that the watch in the dial up position is running quite slow at 71 seconds per day. It had very low amplitude (degree of rotation of the balance wheel in each direction) of 184 degrees. This is considered very low on a full wind for a movement of this type. The amplitude gives you an idea of how efficiently power is transferring from the mainspring, through the mechanics of the watch and into the balance. The less power getting to the balance, the lower the amplitude you'll have (also must take into account the pivots on the balance itself – which are critical). It had a beat error of 2.8 milliseconds. The beat error is the difference in time between the clockwise swing and the counterclockwise swing of the balance. That isn't really all that bad for a vintage watch, and would be considered acceptable in some standards. If the watch was keeping good time, but still had a beat error of 2.8m/s, many watchmaker's wouldn't even bother with it. I suppose my OCD is a good thing when it comes to watchmaking. I knew that if it was 2.8 to start out before any service work that I could get it closer to 0 m/s, which is the ideal. Technically speaking, anything at 1.0 m/s or lower would make no difference in the watches ability to keep time accurately.
Here's a few pics of the initial tear down:
Continued on next post.
Last edited:
