lol This just struck me as funny. Who says microscopists don't have a sense of humor?
Micro lenses for photography
Micro lenses with microscope thread mount:
For high quality macro- (1:1 - 10:1) and micro- (10:1 - ) photography, normal macro lenses are not sufficient. In this range of magnification, special micro-lenses are required.
The thread mount of most of these lenses is known as RMS, the Royal Microscope Society's proprietary thread, with the specification: W 0.8" x 36tpi (1/36")).
This thread is generally known to microscopists as the "Royal screw", and I suspect they don't get the pun at all.
Below a listing of all existing micro lenses (current and historic) for photography.......
http://www.markerink.org/WJM/HTML/microlen.htm