How many of these were made? Also, does anyone have the specs? I can’t seem to find them…
Note I had no idea where to post this, so feel free to move it if necessary (as if the mods need my permission). 
I believe the specs are as follows:
51.25 OD
44 width
4.1 gap C bearing
Silicone/Hat Pad response
62.5g
I’m not sure but I think 30 were made as a result of a machining mishap when producing the Flying Huts. I think each was individually ano’d.
Sources - some cheeky googling, HSYY and my case
Awesome, thanks for the info! 