One thing to try is take pics and post them on here. Make sure to get fairly decent images. Some folks may be able to ID the parts for you. As with the amp rating of an esc, look at the input wire gauge and motor wire gauge. Usually the battery leads will get you close.
My 100 amp hobby wing uses 10 gauge. But so does the 60 amp. This will only get you close or ball park.
Also if you know what heli those escs were on you can get close. If they were on a 600 and up class then chances are they are 120amp or bigger. A 550 class is going to be around 100 amps, a 450 (360) class 35-60 amps.
Hopes this helps.