1903 Mark 1

New to this forum. Lots of good information here. Thanks.
I purchased a Mark 1 for my son for his birthday in February and have been obsessed with it since. Defiantly my favorite gun ever and it's not mine! It was somewhat molested over the last 100 or so years and I've tried to make it what it was. The guy I bought it from said it was a good shooter, clean and only had a few minor changes. Well we put a box of 20 through it one weekend after a good cleaning. This one is as much fun as the 30-40 I inherited from my grandfather back in the early 90's. The serial number matches the date stamp on the barrel of 2/19. The bolt does not and I'm looking for a J5 incase any of you have one for sale. Someone put a side mount sight on at some time and it appears to have been a Jaeger with 3 1/8 spacing between the mounting holes, if someone has an undrilled Jaeger side mount that's at least 3 1/4 total width I'd be interested. There are some markings I was hoping you experts could help with. On the barrel under the rear sight a "W" is engraved in the top and bottom. There are several stamps on the bottom of the receiver opposite of the serial number on top. T, 3, R, C, at least that's what my old eyes see. I've bought the correct trigger sear for the Mark 1 and a few other items such as headspace gauges. Have to say from what I've seen the gauge should be removed with a magnet but both bolts I have I need a wooden dowl and small hammer down the barrel to unseat the go gauge. Is this normal? With the no go I cannot close the bolt. Both are with the extractor removed. Also looking for a dated 1919 original usable sling. The stock was not ground around the Pederson ejection port as in pictures I've seen but was ground for the side mount. There is a "3" stamped on the stock at the forward triggerguard mount hole. Also a "O" stamped inside at the rear stock collar and 7246 stamped near the buttplate on the left side. Any insight on this would be appreciated. Thanks.

I think most of the letter and number stamps your seeing are unknown sub inspector marks as the rifle was being assembled.
The 4 digit stamp in the butt stock might be a Greek mark denoting the last 4 of the serial to whatever receiver was in the stock during their possession.
The go gauge is really only needed for chamber reaming a new barrel. your'e fine with passing a no go.
Congrats and enjoy it.

You should not apply any pressure on the gauges. Insert the gauge and with the bolt STRIPPED and then take the measurements. Only apply very gentle pressure on the handle when closing.. The bolt should not close on a no go and close on the go gauge.

Thanks. I did strip the bolt and it closes fairly easy with the go gauge, but the gauge does not fall out as I've seen in videos. I have to run a wooden dowl down the barrel and tap it out with a small hammer. The bolt does not come anywhere close to closing with the no go gauge.

Maybe a good scrubbing of the chamber will help that issue.

I've been trying to figure what mount was installed on this receiver for some time and can't figure it out. Could the armory have installed a mount or is this a hack job by a civilian?

The armory definitely didn’t do that.
It’s likely a Weaver or some such mount.

Weaver, Paul Jaeger, and others I've seen are less than 3 inches total. The hole spacing is 3 1/8 with overall 3 3/8.

I once had a Remington Model 8 that had 13 holes drilled in it for various scope mounts over the years.
Point is, the overall hole pattern that is currently present doesn’t necessarily represent one single mount.

Understood. This one has the two outer holes with threads and the two inner holes without, assuming for dowl pins. This leads me to believe it was a mount similar to Paul Jaeger or Weaver but the hole spacing is too far for either.