Finally got that one.
1675 Mk4, 1978, perfectly unpolished, original hands and lume.
I just (!) have now to find a red back insert from that period (the current one is just a little bit later, beginning of 80's, with a blue back. But I love its Pepsi red&blue... Not sure to find a nice red back like that...)
Picked up an 80's Swiss (Brevet) made scubapro diver 200 on marketplace for $25.
Apparently, they only made these for 2 years and most were black pvd. Not a lot of info out there and will likely be impossible to source a bezel insert...
Movement is clean, and I haven't tried a new battery yet but fingers are crossed.
It's been worn a lot, but it's a cool enough piece for the loot.
Snagged a blue 6119 for surprisingly cheap. I've got a growing stack of 6119, 6106, and 5126s that need some love... Might take a box of them to the watchmaker later this year.