I noticed on the KEH site that they have two different types of Hasselblad A12 backs. They have A12 backs and then they have A12 backs with 12 release. What's the "with 12 release" part?
I think the 12 release is the older style hat have a 12 imprinted on he release button. The newest style have built in darkslide holders and say A12 or A24 etc next to the release button.