The 'Ribbed Grey' roof model was first introduced into the range in America, but in the U.K. it was introduced as part of the 'Giftware' range, so was plated with the 'Chrome' effect finish and mounted on various trinket boxes or ashtrays. It was also pointed out that the rear side window frames were being damaged with the top corners being bent inwards.

Note the top corner of the side window frame, it is bent inwards.
A modification was done to the inner side rail of the roof component that added a small lug (collectively now called a 'PIP'), and by putting one of these 'PIPS' each side on the roof, it helped prevent the top of the window frame bending inwards. The drawings below show where the 'PIP' was added.

No 'PIP' and with the 'PIP' added.
Because of this modification, the story of the Y-7 Rolls-Royce gets confusing, because it was discovered the models without roof 'PIPS' only appeared in America for a very short period before models with roof 'PIPS' started to appear and models without the 'PIPS' suddenly bacame very collectible and scarce.
Examples without roof 'PIPS' started to fetch some serious money and of course, the fakers got in on the act by faking such models. The clever fakers found out that 'Chromed' models from the 'Giftware' range could be found with the roof 'PIPS', so all they had to do is remove the roof from this and transplant it onto a normal painted model! What the fakers did not know, even the clever ones, the genuine NO 'PIP' model, had other identifying details around the baseplate and chassis and if as a collector you knew what the difference was, you could tell the genuine model from the faked model.
The not-so clever fakers just used roofs of any old Y-7 Rolls-Royce and ground away the side rail 'PIPS' and repainted the roof in what they thought was a matching metallic Silver-Grey and often just glued this onto the model and when one of these turns up at a toy fair or in a shop, it is quite alarming when inspecting the model and the roof suddenly gives way and snaps off from the body!!
GHOSTHUNTER.