When did the stamp of 925 replace the term of sterling on sterling jewelry and other items?

I think you're referring to pieces that don't have the 925 mark. .925 & 925 have been used in America since about 1856. "Sterling" has also been used much longer than that. In 1973, the new Hallmarking Act dropped the decimal (.) from in front of the 925. That information is helpful when dating a piece!

"925" does not have to be marked on a piece if it has "Sterling" or an abbreviation, such as STER. Alternately, if there is a mark Some makers decide to put both 925 and Sterling.