squeeler, I can't tell you but I know they were still present in 1966. I suspect sometime from there until the early 70's. I know, no help.
This rifle has the same folding sight I had on a 1958 308F I had.Guess I'll wait and check the date code on it.It's a 270.
Catalogs stopped showing barrel bosses on 110's in 1968.
But it could be cartridge specific, like the 99 in 284 never having a barrel boss. Such as the 1966 catalog says 110's in 22-250 have heavy weight barrels.
Found info,1958-65 had the boss.
Has any wrote a book on Savage 110s?
Someone other than me should it.
The first bunch of 110P in the '80's with the weatherby-esque stocks, had the barrel boss, then at the end of the 110P they did not have it.