How rare? Well I don't actually know. I've seen hundreds of posted frame movements and I only know of four with eight day clicks, two by John Knibb of which I own one. This one has a slightly different look to the others, it looks less like an 8 day click, perhaps more like a date wheel. However how rare is the question, because I had already listed this one on ebay for parts before I realised what it was. I've owned it a long time, it has been knocking about on the floor of our conservatory collecting dust and unloved. It came in a lot of three clocks of which I wanted only one and had to take all three. The other has also been sold and the one I wanted has been fully funded by the other two so I can't really complain. It already had a bid on it, and being an honourable chap I let it run. It sold for that maiden bid, even though I had updated the description and also found the bell stand which I had listed as absent. The movement is rather nice anyway, has consistent collets, so not messed with, has round posts, an unusual style of chain sprocket that grips the outside of the link not with spikes and therefore not affected much by chain stretch. All in all a bargain for what it went for, but everybody is entitled to a bargain. At least I took the pics and can list it here for posterity.