This is the last Geomorphs set.
There were 3 more sets for future release that never happened – Castle/Fortress Outdoor Geomorphs, Ruins Geomorphs and Rooms, Chambers & Passages. They appear in the product list on the last page of this set and the 2nd printing of the Holmes Basic D&D book (in the product list on the back).
As to the content, you’ve seen one, you’ve seen them all.
This one has quite a bit more text than the others. Basically it gives instructions on how to create a realistic city or town, describing all the things to consider like history, government, divisions (eg thieves quarter) and a huge list of occupations. It even gives lists for things like building types, religious buildings, street types, etc.
The example keys are very elaborate, even with descriptive pointers to other non-existent keyed areas, eg “See #56, Society of Sages, for details of … “ and there’s no #56.
Design-wise, the major improvement is that it doesn’t use the typewriter style font that the other ones used.
The copyright was registered as June 12 1977. No reason to disagree. It appears in Judges Guild issue O from Oct/Nov. It’s also on the back of the 1st printing of the Basic Set.