Hi Dave,
It's a minefield.
Would you believe I've had one with the triangular tips missing from the PCB clips making it completely useless (the seller tried to avoid refunding me but eBay overruled them).
The operating boss on the reverse of the buttons was too tall on another so that (1) the PCB couldn't be secured under the clips and (2) with the back cover attached the microswitches were permanently pressed!
The seller refunded me claiming that he'd never before had a problem.
All of them seem to have had the platforms and shoulders removed from the transponder box so Blu Tack has to be used to stop it falling out.
The finish on the exterior is always very good, it's the changes and roughness on the inside that's the problem. There's an opportunity here for DMGRS. I'm sure we'd all be happy to pay more than £5 for a high quality copy.
Simon