Earliest type (like the red one) has the 'slip-in' plastic catch mechanism (which tended to harden up and break...) and these were replaced by the spring steel screw-on type.
I'd have to look up the changeover point, but it was pretty early. During 1970 off the top of my head...
Thanks Alan. Dont bother looking it up for me. I thought it might be from an "early" car.
Pity really its different cos its in nice condition.
I must have picked it up in a clearance deal somewhere along the line????
Another random sale thread coming up!!!
Or bung it on Ebay .....sold as seen LOL!!