I looked around online and found various reports of requirements. Some say it is required to have it on the gun at all times. Others say its not and you do not have to produce the stamp on spot, just have the ability to produce the documents in a timely fashion. I'm curious if a PDF copy on an electronic device would be acceptable. Currently I keep the original stamps in the safe. I have made a copy and keep that in my range bag. I also saved a PDF version on my secure cloud, just in case. Could I just keep the digital copy on my phone and not carry a paper copy and be in compliance? Only reason is to reduce clutter in range bag and increase personal identification security.