Hi Corduroy,
Well that's one of those things that one wouldn't pick up on unless the item was directly in ones hands so as to compare apples with apples.
Must admit I wasn't aware of any minor changes like this in the transmission area between Rover and Scott Bonnar, but one must ask the question, who's been in there before yourself and messed around with something they didn't understand and also how did they tolerate it with it running like it did in constant drive and using the primary clutch to disengage the land roll.
I'm thinking that someone substituted the part that the cork is bonded to some years back, opposed to just replacing the cork itself on the original component. From there they've just learnt to operate the machine with a quick flick of the primary clutch in and out.
The downside is that the only way to obtain the correct part is sadly at the cost of another machine being wrecked. Probably best you find a cheap electric Model 45 of which there are still plenty out there going for no more than $50 and use the land roll clutch out of that along with a whole lot of spare parts to put away, then finally cutting the chassis up for scrap as they are not easily convertible to petrol without a lot of welding involved and relocating the engine mounting points as electric are further outboard than it's petrol counterparts.
Anyway it's good to hear of an outcome and it has brought this small abnominally to our attention.
Cheers,
BB.