Vintage Double Hose

In an earlier post I wrote about the conshelf supreme I found NIB on ebay. I just got a conshelf 2nd from bryan to use as an octo. Just rebuilt it, seems pretty good I'll dive it tomorrow to test it out. I noticed that the serial # is proceded by 81 on the ebay purcace & 78 on the VDH purchace. Is that the year of production??

It has been my experience that yes the first two numbers (at least during the period that you are referring to) do represent the year of manufacture. Later (and earlier) years are not always so presented.