The design was unchanged since 1931. The motor that went with it was similar to E20B long plates with carbon mountings outside the plates. Notice the fabric-covered mains wire and the wooden base , face and rear plates -in 1970! The vent holes to the Meccano standard invited to put a bolt thru them.. There was an auxiliar 4,5 V supply in the rear for lighting. It should have a metal plate with the brand Meccano and the rating glued behind the cursor, but I removed it and lost it when I was a boy.