Ross XPRES f/4.5 6 inch (152mm) large format lens, #11683
The lens is purposed for large format cameras, so it will cover any existing sensor and any upcoming for 50 years ahead :-)
Can't find reliable info on it's design. Seems to be symmetrical (double Gauss) since flange focal distance is about same 15cm in usual and reversed direction.
Glass is in surprisingly great condition for its age - just few cleaning marks and dust particles.
Aperture ring works fine. Diaphragm blades are dry.
Mount thread is quite unusual - M47.5x1. We can make adapter for some other thread if necessary. For example, you can mount it onto M58 Chinese focusing helicoid with intermediate tube to match flange focal distance and reach infinity focus.