80s cranks usually used 52 or 53t large rings. The smallest cog though was larger than today's common 11t, so it balanced out.
As a result, 50t chainrings arent nearly as common then as they are now.
48t chainrings though- those were all over the place due to touring bikes and the 1st decade of MTBs using 48-38-28 triples.

With that said, I have a couple of 50t chainrings that are from the 80s...though one is Ovaltech(biopace competitor), so they were around in some volume.

The new 5arm Sugino rings are quality for the price. Also, Shimano 5arm chainrings can be found on ebay both new and used often for good prices. I used new Shimano Ultegra 34t rings for my compact doubles- they were $11 on ebay.