As far as I know, there are two different castins for the boy of this bus, both are based on the Leyland STL. The chassis are the same for the two models.
The earliets bus does not have a roof box, it has small front windows and ridged hubs.
The later has a roof box, larger front windows and ridged or spun or plastic hubs.
This model was a promotionnal distributed by both Chloride Batteries Ltd. and Meccano Ltd. at least 100 000 were made.
... and the same development goes for the 'regular' double deckers 290. They got wider front and rear top windows too and lost their number 290 cast underneath as soon as this casting had to be shared with 291. Some pictures attached. Kind regards, Jan
The ref. number 290 does not seem to have been erased from this 291 casting. It is probably a different mould. There must have been several..