Brand new 50mm diameter 4-jaw self-centering chuck has reversible jaws.

You can select the WW style thread .270 x 40 fit most all 8mm lathes such as:

Bergeon, Levin, Derbyshire, Boley, American Watch Tool Co., Peerless, Marshall, and most others.

Or metric size M7 x 0.75 such as Vector and HOROTEC German brand.