I have a few NOS moving iron ammeters, the sort with a compressed low end of the scale. The ones you always see in the bottom of boxes at rallies when all the decent moving coil ones have sold.
I have always used these as seemingly designed, for measuring AC current, but I needed a DC ammeter for up to 20 Amps, so tried one. It seems to work fine on DC, although dampening is not great. Up to the 10 amp DC current limit of my multimeter the two track fine. Is there any reason *NOT* to use one on DC? I even noticed the terminals are marked + and - on some of them ....
Thanks.