Close-up of the Hi-Speed warning stamp showing what looks like matching faded finish in the protected areas and raised edges, other stamps on the barrel appeared to have been done before polishing & finishing and have more finish left in protected areas-
I have seen the same warning stamp on several 1903's & 1914's and on one 1912, pictured here, all appear to have used the same roll stamp. Hi-Speed was not introduced until 1931 so this stamp could not have had to been applied to a 1912 until at least 15 years after this gun was made -
Savage/Stevens models that could not handle Hi-Speed that were still being made in 1931 and later were stamped 'REGULAR CARTRIDGES' somewhere for a warning when they left the factory, this stamp will be found on the last of the Savage Model (19) 04's and the weaker actioned Steven's models, including Visible Loaders as shown here -
My thoughts are that this gun was sent back to the factory for repair about 1940 or later and it required a new receiver, and even though it was an earlier model, for some reason they stamped the receiver with the stamp they were using about that time on the newer model, possibly it wasn't supposed to be stamped but got mixed in with the other receivers. This also would have been when they added the Hi-Speed warning stamp on the barrel.
Here are comparison pictures of two 29 actions showing why I think it might have needed a new receiver and why they added the Hi-Speed warning - the lower one shows damage to the locking surface I think was caused by Hi-Speed cartridges -
The distortion of the locking surface also starts to keep the bolt from raising to fully engage the locking surface and eventually could get to the point were the action would not close far enough to lock up. I think any play and any reduction in locking surface engagment would cause the damaged to progress very rapidly once it started. The example pictured is not the worse I have seen. You can check the locking surfaces for damage by looking through the ejection port.
According to JTC Savage made changed to the 29 action in 1931 for the use of Hi-Speed, from what I see the changes were just to better support the head of the cartridges and there were no changes to strengthen the action, unless they hardened it different or something, which I doubt, that's why I do not recommend shooting Hi-Speed loads in any 29 action.
I think the 29 was based on old expired patents for a design from 1912 and that is why it is one of the few Savage guns from the time that never had any patent information stamped on it - until they expired the patents were the property of someone else - first Sears & Roebuck and later Mossberg. Here is one of the Mossberg manufactured examples, you can see the similarities in the design to the Model 29 with all internal parts similar in form and identical in function, even down to the ball bearing cartridge release that was not in the original design but was introduced with other changes by Mossberg... and the same issues with the locking surface -
There are a couple patents for this action in the names of two brothers, but I think their father actually designed it, although there were inherent problems with this design, the father did have one earlier design that still has a very good reputation!