Not quite to the subject, but I bought a 10-7 with all the (bad) characteristics of 1980's Smith production, but it had a C prefix serial number that would have placed it in the early 50's (turns out the original shipping date was 1952). Apparently Smith would use the same serial number on a replacement gun if you sent one in for repair that was, well, beyond repair.
Richard and Mike are right, the 10-7 was made for quite awhile, from 1977 to 1988 and they are as common as mud.
Best,
Bill