I have in my collection a Belgium 25 Centimes 1946 coin (KM# 132) with a diameter of 24 mm, which is exactly 2 mm smaller than the normal version. The coin weighs 5.36 g. (6.5 g. for a normal one). The coin is in my opinion UNC quality and does not show any damage as a result of any manual handling. The center hole is inside also without any damage.
I'm guessing this isn't a PMD example, either, nor is it counterfeiting.
Could this be a coin struck on a wrong blank coin plate?
I'm of course very curious about your opinion...