WinchesterOwners.com

Welcome to the forum jut.

This from the Winchester site under historic products. Does not mention YOM. "The legendary handling and quickness of the Model 70 Featherweight is justly famous among hunters everywhere. The Model 70 action is highlighted by a jeweled bolt and knurled bolt handle."

Welcome to the Winchester Owners Forum Jut Hale !!

I believe you have the most probable answer in the possibility of a replacement bolt handle. Yet to not to discount the abilities of a skilled craftsman. Without first hand observation, difficult to render a good opinion, but as you note, in any case the bolt isn't original.

The Winchester history available at the current Winchester-FN site is thumbnail and sometimes either incorrect or more an exception than a rule. Yet never intentionally misleading that I've noted.

The pre 64 Winchester Super Grade rifles normally bore factory 'jeweling' on bolts; other models did not. Of course, through much of the production life of the genre, a custom order might have easily included jeweling.
You apparently have access to Roger Rules great book... A thought! Check to see when the hollow bolt ball became standard on the Featherweight model. By 1955 production, it should have such feature. IF SO, almost certainly the bolt shown absolutely incorrect for your rifle.

My take

I can think of one explanation as to why it was changed.... I'm not a model 70 expert by any means, so its really just a guess..... After seeing the photo above from your previous post, here's what comes to mind. (I haven't seen pictures of your actual receiver, so I'm making some assumptions here that may be incorrect.) My guess would be solely based on the assumption that your 1955 has a similar configuration with regards to scope mounts or the receiver has been drilled and tapped on top for a scope. If its not drilled and tapped, then this theory is out the window.. This is really the only reason I can think of for changing it since an original pre-64 rounded bolt handle wouldn't have worked with a scope mounted like this unless it was machined flat on top. I've seen quite a few of the original pre-64 style bolt handles that have been machined flat on top so the bolt has clearance to the objective tube of a scope with similar mounts. A post 64 style bolt handle that is already flat on top with a profile that works with a low mounted scope might be an easier fix than machining so maybe this could be an explanation for the change.

From the pictures, I can see evidence of welding. Look at the color of the metal. It has been heated to a high temperature.
Excellent workmanship!