U might try the servo on a digital system, eg. HRS. If the servo survives, it's digital. If it fries, it's analog. As simple as that.
However, if u fry yr servo, I don't think the Administrator will reimburse yr loss due to giving false information.
Good Luck. Pal
Disclaimer : I'm not responsible for any property damage or injury if u choose to experiment by yrself.