They are given numbers.
The vertex couplings are 19, that's the PCL type.
There is a 17, which is a stubby thing, you find on old engine analyser's, well that's where mine came from, think that might be the scharader type mentioned.
Type 23, theses are the Dyna-con connectors which norgren and snap on flogged, this is what I have. Then the larger 23's, they are 25's and probably what you call euro.
The hydraulic shop catalog, forgotten the name, has pictures of the most common ones, with the makers part numbers. Flotech was the name I was looking for, the catalog is online.
There are vast differences in quality, hardened steel bits from Dyna or CEJN are still good after 35 years of being hurled across garage floors, cheap stuff lasts week of constant use and doesn't put up with abuse.
Ditto; one useful thing is that Machine Mart sell genuine PCL and their own version which is interchangeable, so if you get stuck for a fitting on a Sunday morning you know where to go (albeit a bit spendy compared to what you pay via Ebay).
I can also vouch for genuine PCL, also genuine Schrader, I like this type because the collar is twist to release. Also Snap-On / Dyna Con.
The Staubli are superb, probably the best QR pneumatic connectors available but rarely seen and expensive.
We use Legris connectors at work, long lasting and safe as they vent line pressure before releasing coupling saves having airlines whipping all over the place like some QR couplings