It's already been described in this forum the Mayflower 816 80mm x 1200mm that I picked up on EBay. I tested the optics during the daylight using an antenna at some distance and I wasn't really pleased with the results. I couldn't bring it into a good focus. Furthermore, the Newton's rings were way off center and the objective was quite dirty between the lens elements. I had tried to get the lens cell "set ring' loose to clean it and adjust the spacing, but couldn't budge the darn thing. I picked up some Liquid Wrench and used a technique that I had seen on the Binocular forum to carefully place the LW just where the ring met the threads on the cell.
While doing that for the second time around, slowly putting the LW on the ring (because we all know how frustrating it is trying to clean oil off of glass) I noticed something I have never seen on a telescope objective cell before. Embedded within the threads of the cell was a darn grub screw. I've seen plenty of those when repairing binoculars (and expect to find them everywhere), but I've never seen one in the threads of a telescope objective cell. Someone must have really wanted that set ring to remain in place. I mean, what the hell did they think was going to happen to loosen the darn set ring that they had to put a grub screw in there!??? It's no wonder I couldn't budge that ring with my spanner wrench previously! Once I loosened the set screw, the ring came right off! The 2nd image shows the set screw.