I've seen Model 53 paperwork advertised on GunBroker and eBay recently. Not sure if it is original, but you can check it out.

I have a six inch 53 that l like to shoot and reload for. It's not difficult. I use the Remington cases, .223 45 grain bullets, Federal small rifle primers and WW-296 powder. I load the cartridges somewhat less "hot" than factory loads and it is quite accurate. I recently found a .22 LR cylinder for the gun (correct length) and intend to try it out soon.