How to tell McIntosh MC452 and MC462 difference

The newer model has different transformer covers.

Thanks Russ!

The reason I asked was not for sound quality. I asked because I heard that some unscrupulous people are selling 452s with 462 badging.

Well, the unscrupulous people would have to go to the trouble to replace the glass on the front, since the model number is right on the front below McIntosh.  

Not exactly what you were asking for but If cost (savings) is a factor, you might find a demo 452 still for a lot cheaper than a new 462. The audible difference between the 2 is negligible from all I researched. I was able to score one for a lot lesser than a new 462. 
 

Just received my 462 yesterday. Time to do some experimentation with differenc components.