Yes, that can be a problem. I have a lens, which I know is a JML 10mm, but there is no lettering or numbers on it at all and it is in a cylindrical barrel with no mount. I have another lens, a bit larger but otherwise similar, with no markings or mount, about which I can remember nothing.
Female with much smaller male and flies.
Olympus EM-1 Oshiro 60mm f/2.8, 2:1 LD UNC Manual Ultra-Macro, f16, twin TTL flash, hand-held.
P6301391_DxO Misumena vatia with Male and Flies Oshiro 60mm 1 to 1 Topaz 1024.jpg
Olympus EM-1, Kiron 105mm at f16, twin TTL flash, hand held.
June 2016.
P6302624 Crab & Fly Kiron f16 Twin Topaz 1024.jpg
Sony A7r3, no extension, Rayfact RJ 90mm f4 at f11, hand held.
DSC06441 Abutilon Rayfact 90mm f11 Crosseye 1024jpg.jpg
Dial it UP-side-down! by simple.joy, auf Flickr
(Zeiss Dokumar 5.6/38)
Gran exit by simple.joy, auf Flickr
(Tomioka E-Yashionon DX 3.5/21)
Guidance system by simple.joy, auf Flickr
(Schneider Kreuznach D-Claron 3.5/30)
Mycena? on damp cardboard.
EM-1, 100mm extension, Luminar 63mm at approx f16 "15", FOV 5mm, twin flash, hand held. Image cropped slightly.
_5094920_DxO Mushroom Mycena Luminar 63mm f16 1024.jpg
Olympus EM-1, 100mm extension, Printing-Nikkor 105mm at f11, ISO 200, FOV 35mm wide, hand held.
I must revisit this flower when the pollen is ripe.
_5094907_DxO Columbine Printing 105mm.jpg