Hi Mat,
Well the engine was manufactured on the 17th of November 1993 and if it's the original engine then I'd say the mower was assembled around March even April 1993.
Could you please furnish us with some photos of your Rover Red 45 and especially a close up of the ID sticker.
If you can take the chain case off you could also take some close up shots of the drive train and thus we could assess that for you as well.
The more photos the better of a picture we get to give you feedback.
Cheers,
BB (also at times RB)