Update on the 7150 meters I brought at auction last week, both have now had their mains filters swapped out after one spewed up last week releasing its toxic magic bleeding smoke.
Both of these meters running for some hours now, along with other main meters and it seems that one is calibrated well and the other is still good enough for my requirements seeing as its about 1mV high on the 10v range. I'll have to look in more depth in the SMM but I don't think that it's a meter that I can calibrate with my gear, its software driven I think.
I have to strip them down again in a few days when the parts arrive to provide better LCD illumination so I'll check on the rail voltage for each range then as these I can control via a few trim-pots. Otherwise it would need a full re-calibration by someone else. As these photos show, It would seem that I got a pretty good deal overall as these meter have been going on eBay over the last few months for around £200 each, way more than I paid including all fees for them both, so I'm very pleased.