Mike - EXCEPTIONAL!
The story goes that when the badge was first issued it received a great deal of criticism from outside the unit - not seen that drawing before!
I am very fortunate to have a couple of attributed ones - here is one.
Worn by 2 SBS only. As you say - a very small unit - Nominal Roll in Geoffrey Courtney's Book 'SBS in World War Two' suggests about 34 at Saltcoats in 1942 before reinforcement at Hillhead 1942-43 of about 65. Far fewer names by the time of posting to Far East - A rare thing.