Foxy;
Two things I'll have to disagree with you on.
1st that WRA developed the idea of building different gauge guns all on the same frame. Several makers had been doing so well before the 21 was introduced. In Fact, many of those so-called parker frame sizes are not truly different frame sizes at all, only the standing breech & consequently firing pin spacing was varied to accommodate barrels of different weights.

2nd a GHE with a single trigger is rarer than a GH with double triggers, just as a double trigger 21 with extractors & splinter forend is rarer than a 21 with ejectors, beavertail & single trigger.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra