Are you in Canada? Apparently certain places in Canada (I believe Ontario at least, but perhaps others) require the entire cabinet be run off an isolation transformer. The story I heard was that some poor kid electrocuted himself due to an improperly wired/grounded/faulted (i.e. triple failure) cabinet in a wet location once, so the legislature somewhat naively required them on all arcade games going forward. If that's where those came from, they probably are indeed isolation transformers.
Easiest is to just check as above. If the primary (input) shows any continuity to the secondary (output), then you've got an autotransformer. If it reads open (infinite or very high ohms), then you've got an isolation transformer. If the output and input voltages are the same, then you've probably got an isolation transformer (since a 1:1 autotransformer is pretty pointless).