Whatever it is they will work for growing, they're identical to units made for growing just in a different shape. Mod it all you like, it'll work with a remote reflector or a cooltube. Stick a fan on the ballasts though, they run hot without proper airflow. Also you may just want to leave them alone and use as is but with the reflector off in a vertical grow arrangement.
They go pretty cheap all the time on CL and ebay, so they're not really that valuable.
If bulbs are in them that will tell you which type of fixture you have, so will the model number I can tell from that. Look at the bulbs, are they skinny or fat? Take one out and look for a marking like LU1000 or Lu400 or m59. It'll also usually say that lamp type on the ballast label. LU is HPS, M is usually standard metal halide.
If they're really new they could be pulse start halides, if they're really old they could be Mercury Vapor. Whatever it is, if it's not HPS and you want HPS, it could be modified by adding the appropriate HPS ignitor. (And maybe you'd have to switch the capacitor too.) They are all almost identical.