How to determine a current is AC or DC by use of analog multimeter?
I haven't used analog meters in quite a while, but I kind of recall that they often have a different selector position for DC and AC, at least in volt mode. So that would be one way.

Another way would be to use it in volt mode, and compare a direct reading with one taken with the meter in series with a diode. If the voltage drops by about 1V, you have DC. If the voltage drops by half, you have AC. However, this may not work with small signals or slow AC frequency.