The 10.000000 MHz reference board I was given [
https://www.eevblog.com/forum/testgear/list-your-test-equipment-score-here!/msg1240933/#msg1240933 ] uses EURO style backplane connectors, with coax inserts.
To have one connector for playing with the reference card, it's necessary to extract the coax connectors from the backplane. Something that I gather requires a very specialized tool, that I don't have.
Here's an improvisation that works.
It needs something that can be pushed down into tiny slots to release the spring retaining clip. I tried a few kinds of sheets of stiff insulating plastic, as used as barriers between PCBs and metal chassis. The one that worked is 0.25mm thick, and quite stiff.
Cut four little strips just under 2mm wide. While pushing the coax connector forwards (towards where the card would be, to free the sharp rear edge of the spring from the plastic connector body) use small flat-nosed pliers to shove the plastic strips into the four slots around the connector. Push hard, rock and and rotate the coax back and forth to help the strips work down and compress the spring.
Once they won't go any further, use a small screwdriver to lever the coax connector out to the rear. It still takes quite a bit of force, but does not break the connector. Rotating the connector some more helps.
This was the first time I was able to successfully remove these things from connector bodies. Eight out of eight worked. So I'm quite pleased.