3/8" to 9/16" HP Port Change?

[Akimbo]

Could the hose manufacturer have driven the port size decision?

I like to think that long-overdue common sense drove it and making them the same was an oversight in the beginning. There haven't been many changes to the [-]standards[/-] conventions in diving that were so quickly adopted.

 

[macado]

They made adapters that go from one size to the other. They are hard to come by. I have some.

Dive Gear Express has most any adapter you can think of.
https://www.divegearexpress.com/regulators/adapters/hose.shtml

Yup, can confirm; ordered a few from DGE a few weeks ago. LeisurePro and VintageDoubleHose also sell them as do others. Any Trident dealer should be able to order it.

I've got a couple ScubaPro MK5s (3rd gen from 1978-1979) and a Voit MR-12 with the 3/8" HP ports that I still use with adapters.

 

[The Chairman]

I remember my regulator from the sixties, as well as my tank had tapered pipe fittings. I think it was a Healthways. Thinner walled hoses have made the need for a 1/2" fitting unneeded.