The Mercian appreciation society

All my pictures are rubbish.... It's one of those things that I want to learn how to do! I'll post some better ones when I borrow my wife's camera... It's at the school right now. The serial is 66991 or 16699, so, depending on which way is the correct way to look at the number, and whether the first two, or the last two denote the year, it's a 99, or 91!
I've not been able to work it out!!

Probably the best one I have of it......

I've got to get those wheel re-dished to suit

Could it be a 66? I read somewhere that Mercian can reverse the frame numbers sometimes and the first two digits are the year. The mounting brackets for the lights seem older than 91, unless someone specified them??