Canon zoom EF lens 70-200mm won't lock on to my 1100d

[Lenkian]

Hello. I have recently found my old EF 70-200MM lens and I was quite happy about it. But when i tried to mount it on, it didnt lock in. It only twisted for 5mm. The second pic shows how its in, the first shows how it should be (just inside the mount). It just stops. Keep in mind, a repair is not even an option atm, dont have any money

[jrhoffman75]

The mount design, red dot, UXXX serial number and lettering on the ring around the front of lens all look like Canon. I think the OP is just trying to mount it incorrectly.

[Tronhard]

I got to this quite late, but to me it looks like the OP has incorrectly identified the lens.  It looks identical in shape and configuration to the Canon EF 70-210mm f/4 lens - this model was first released in 1987: see HERE  There is also a 70-300 version of the same age that looks identical. I got one of the 70-210 units with a vintage EOS camera. 

It should fit onto the body 1100D body without an issue - mine fits on to both my FF and APS-C DSLRs fine.   Actually, it is a good lens for its age and my copy is quite sharp, but it lacks IS.

I am wondering if perhaps a screw is slightly undone and is sitting proud enough to foul the engagement mechanism.  Otherwise all I can speculate on is that it is being installed incorrectly - red dot on white dot?