This Pentac 8 inch (~203mm) f2.9 lens is a large, unshuttered aerial lens originally designed for the UK's Air Ministry: it's the British* version of the Kodak Aero Ektar, more or less. This one's in good condition overall, with some paint and finish wear, stiff diaphragm, and some light surface etching on the rear element: nothing too dramatic, but you can see where someone has wiped it down with something they probably shouldn't have. Clear otherwise, though! Pretty good for something that used to hang off the wing of an airplane.

* Apologies if I have trodden on any sensitive regional distinctions here, I am just a lil' canadian baby.