That sn does not appear in S&W data that I have going up to 1983. You need to call S&W.
The Smith & Wesson Model 37, known as the Airweight revolver, was produced starting in 1952. The serial number 21JXXX indicates it was manufactured in the late 1970s to early 1980s, as the "J" prefix was used during that time period. For an exact year, you would typically refer to Smith & Wesson's serial number lookup or production records.
1976 or so
A shotgun made for Smith and Wesson, sold under the Smith and Wesson name.
The Smith and Wesson model 4053 was made from 1991-1998.
Smith and Wesson does not build rifles. The rifles they sell are made for them.
The Smith and Wesson model 915 was made from 1992-1994.
The smith and wesson model 18-3 was made from 1967-1976.
The Smith and Wesson model 10-7 was made in the year 1977.
Call Smith and Wesson with the serial number and the will tell you.
Standard Catalog of Smith and Wesson.
No. Any manufacturer that adheres to industry standards for ammunition can supply ammunition for Smith and Wesson firearms.
Only Smith and Wesson knows and they aren't telling.