@ Wilko and Charlie,
Thanks Wilko but Charlie may need some more information about his 500C.
A download of the 500C manual with an explanation to load the pre 1968 film backs will get him started I think.
For a download go to
www.hasselblad.se
Register as a user. The 500C is not listed as a camera to register so select the 501C camera and fill in the number of your camera.
This number can be found below the auxilary shutter after you remove the film back.
Then select downloads, go to manuals and select 500C
In the 500C manual the later, post 1968 film back and its operation are described.
Quite a few 500C cameras have the early film back that does not have the winding crank on the RH side.
Operation and loading of the early style back can be found with the 1000F camera.
Do not hesitate to ask questions after reading the manual.
The forum will be glad to help you with any questions that you may have after reading the camera manual.
Paul