Originally Posted by oneclick

They were Carlton (pre-Raleigh) lugs. In 1973 somebody found them in box behind some empty biscuit tins when they were clearing everything out of the little-used lavatory by the stockroom (trying to get rid of the mice they were) and Robboe the foreman made the builders use them and so he sold a batch of new lugs out the back door for drink.

The 1959 Flyer could be had with them, probably other models as well.