Those second stages are IHMO the best second stages ever made. They were in production from the late 60’s into at least the mid 80’s (or maybe the early 90’s, but I am not sure about that). They can be serviced as a basic adjustable demand valve or can be upgraded with the same internal balanced valve as the latest Scubapro G250V.
IMHO those second stages do not belong on a shelf since they can perform as good or better as any regulator build today and they will be far more durable.
The chrome on those looks in fairly rough shape, but they are still very usable.
As mentioned, the Scubapro MK-VII (the honker) can also be serviced and used to dive. The name honker comes from the audible reserve. When the tank pressure gets below about 500 psi there is a honking device that makes a fairly annoying sound.
The Mk-VII was made all through the 70’s and into the early 80’s. The yoke and yoke screw on that one looks like the heavier one from the later years, but it is hard to tell for sure from the pictures.
