It's the first version of the meochrom. The mixing box is definitely different than the ones available for meochrom color-3's etc. It's more spherical, rather than a square looking box. I got a supplier to send me photos to compare and they are different. Not to say they wouldn't fit, but my guess is they wouldn't.

The reflector most definitely isn't built in. It fits in around the bulb, with a little tongue that slots into a little bracket on the bottom of the head chassis which is then secured with a long thumb screw. I doubt it's been modified. It all looks original to me, and certainly doesn't run off mains voltage. I use an external 12v transformer (which I need to check voltage for still - been moving house and my multimeter is at the bottom of a box somewhere.)

Interesting about the bulb socket. How does it affect the performance of the bulb do you know? I would have thought it just serves to mechanically hold the bulb in place. Any idea how I would know if it's causing problems (apart from bursting into flames, obviously)?