The screwmount Pentaxes and the early 6x7 were a lot like the Nikomat/Nikkormat cameras. Except, in the case of Pentax, only the US market got the rebranded camera, because of Honeywell being the importer at the time. The S3 is identical to the H3, except for the H3 saying "Heiland/Honeywell" (on later versions, it was shortened to just "Honeywell"), and the font of the "PENTAX" nameplate being less wide.
The H3v was known as the SV everywhere else. S1a = H1a, etc. The early Spotmatics were marked SP in the Asahi versions, but were unmarked in the Honeywell versions.
Unlike the M42 screwmount bodies, the 6x7 Honeywell version isn't too common. The majority you see in use today or at stores are the Asahi versions.