I came across this clock yesterday in the Ashmolean museum in Oxford, which was labelled as an equation clock but with no technical description. The movement was not visible. It was going and the hands on the main dial were showing Greenwich Mean Time. I looked long and hard at it and just couldn't figure out why it was an equation clock. The subsidiary dial in the arch seemed just rotate once a year. Researching the clock when I got home, it seems it is probably the type which raises and lowers the pendulum thus changing the rate at different times of the year. If so, the hands should have shown solar time and were incorrectly set; at this time of year the difference between solar and mean time is close to its maximum (solar is ahead of mean by about 14 and a half minutes) so rather than showing quarter to four it should have shown something closer to four o'clock. I don't think the museum has a specialist clock curator so perhaps the person who winds it up doesn't realise?