I don't think the model number is on mine... A lot depends on the battery type it will require, as well as other available options....
Mine is a 512 and takes 2 AA batteries...I chose that one since AA batteries can be had most places if I need them and the literature rates them as pretty long lasting..and they are cheaper than the others...
Look at some of the sales listings or their website for the model designations and battery requirements
511s take the "N" battery
552s take the AA batteries
516s take the 123 Lithium batteries..
Some have 'night vision' capabilities where the reticle will not overpower the night vision enhancer.
This website will give you a lot of details..
EO-Tech Info
