Fuel Drain, Yak 52, Heavy Spar fuselage
We're not sure there is a one-to-one correlation, but Fuel Drains, in the belly of the fuselage, seem to fall into two categories - before or after the 59/60 Heavy Spar modification.
This one is short and suits airframes that have the heavy spar.
Earlier 5g (pre-spar mod) have the drain located further aft, and a slender tube to the drain valve passes below the spar. The shape as well as location of the belly sheet metal covers are different also.
All that said, here is one (short style) drain valve assembly that will connect directly to the rear face of the Flapper Valve assembly.
Working when removed.