SubGunSam

Ive locally found a Sten Mk II tube that the seller states is an ERB tube. He states its uncut. Ive not heard of ERB selling tubes before. He also has a sterling MK4 that is built on a Sten tube according to the f4, but has the proper Sterling Cocoking Slot. Im interested in both guns, And Im aware of the Stenling conversions. Is this common?