1220 is the battery size. DR is the chemistry of the battery... but as long as the voltage matches, it doesn't matter. So if your battery is 3V, you should be able to use a CR1220, which is pretty common.
Oops it is a cr1220 that's what I get for not taking my glasses off. they are great for pc but not for close up can see better without. Optician tells me if I live till i'm 150 I will ony need distance again