Originally posted by pathdoc I'm trying to figure out what the SP means on the top cover of my second one.
As far as I know it's just the two-letter model designation that Asahi gave the original Spotmatic. For whatever reason the Honeywell-badged ones don't have the model designation on their top plate, which was a bit of a change from the usual practice of doing so for the pre-Spotmatic models they released. (Though the model numbers did tend to change slightly for pre-Spotmatic Honeywell releases. e.g. the "S2" became the "H2", the "S3", the "H3", the "SV" the "H3v", &c.)
In other words: it's exactly the same as your Honeywell one.