TSR released its espionage roleplaying game in 1980. I don’t see too many of those 1st edition sets come through the shop.
By 1981, they’d re-worked the set into a 2nd edition. Visually quite similar at first glance, the rules underwent some changes, particularly combat from what I can see. If anybody knows of a good blog post or forum thread outlining the rules changes between 1st and 2nd edition Top Secret, let me know and I’ll link to it.
I’ve got 1st and 2nd edition sets to contrast together in photos today.
A noticeable change is the box itself on the inside. Most commonly seen in the Holmes Basic D&D set, early TSR boxes used a box blank with the graphics as a glued-on sheet, both top and bottom. This “glued sheet” box format was retained for a brief time, before being replaced with a box with the graphics printed directly on the paperboard.