Quote Originally Posted by Alan W View Post
I have "matching" and "non matching" backs and would challenge anyone to point out any difference in negative quality-I've never seen any.The older 12 backs have an asa dial at the back that covers a hole which enables you to look at the paper backing on the film-newer ones dont have this.I recommend a look on youtube to familiarize yourself with backs before you buy.
I think the concept of the backs and the inserts matching means they were machined together and QC was such that it was precisely fitted and matched in all gearing and fittings. In most cases it would not matter I'd imagine and I too shoot one or two backs that do not match. I guess with wear and use over time there is a theory that matching ones would take longer before "failing" or wear better as unmatched ones might not be as smooth or the gearing as precisely fit which could grind together though even minutely so. All things being equal if you can get matching numbers do so of course. How much more money for that and whether it's worth it is up to you.