This image is taken from a single piece of mail I just received the other day from a MA State government office, which I found rather interesting.

In addition to the fact that the meter showed postage on the front at 34.9 cents (first class presort) it was backstamped with another 10.0 cents (which is 0.9 cents over and above the 44 cent non-presort first class rate).
First, in that a meter was used, there would have been no reason why the backstamp could not have read 9.1 cents to make up the required first class postage, but instead the extra 0.9 cents was used (and wasted).
Second, two different meters (and different meter manufacturers) were used (Neopost on front, Hasler on back) on the same piece.
Nothing earth-shattering, but it just seemed a bit unusual for a modern day piece of metered mail, so I thought I'd share it.