Hi. I got these from my dad this week. These belongs his father back in the days maybe 60-80? My grandmother was working in goldsmith shops, so these might be bought from there. I don't know what is best solution, first inspect by my self, open case, let some pro to see these, maybe fix these? Some works immediately when moving.
The yellow one with the calendar at 26 is an awful fake. Do nothing with that one. The cost of servicing all of these would be rather high. So maybe choose one or two that you like best, and have them checked out for servicing. The black dials look rather tired. The white dialled one in the steel case might be a good one to check out first. It really is your decision as to what to do.
The fake may have a usable movement (AS1130?), people still use that movement, hopefully it's not engraved Omega. Sell the Cosmic as is. It's just plain ugly. Check the movements on the other two, see what it would take to get them presentable or you may be able to put them on eBay for parts/restoration. Put all money together and get the little 600 serviced/crystal/strap. It's the cherry of the bunch. These opinions of course are based on nothing but the photos provided.
Seamaster 600 looks pretty good.I would definitely keep that one. I would pair with your new seamaster.
Will buy some new straps and but these to watch box. Let them be there. All works so one will be my smaller suite watch one day. Later will check inside all and see what happens there.