Firebox patches are very common. Shay 9 at the Loop has two corner patches just below the tube sheet to replace what was a larger area of pad welding done by West Side Lumber. UP 3985's firebox is made up of nothing but patches, which is part of the reason its now out of service.
I have been in the firebox of a half dozen or more steam locomotives, and every one has evidence of at least one patch. Most have them in the corners, as these locations they seem to get the most "wear". Some others have half sheets, from the mud ring up. These repairs were very common when steam was still running in the 50's, and they tried to squeeze as much life out of the locomotive before it was finally retired and scrapped.
? Unclear what is the basis of your comment.
The fitting of corner patches to the inner firebox is standard documented practice followed by many railroads. As with all significant repair work done at the IRM steam shop we follow such standards in making the repair. Some other preserved locomotives have undergone similar repairs recently and other locomotives in the collection show indications of similar repairs in railroad service.
14th is probably one of the least likely Sundays for there to be people working as the Benefit is that afternoon.
I will check around to see if anyone is planning to be there. The Sunday session normally starts around lunch time.