InterServer won't publish their BGP communities

BGP community reference for a secretive upstream My upstream at InterServer doesn't publish their BGP communities anywhere I've found. No looking glass with community info, no whois remarks, the support portal just says "enterprise-grade routing" and deflects to sales. I'm trying to do selective prepending for certain peers and maybe blackhole bad traffic at their edge. Most providers at least document local-pref or prepend communities, but InterServer seems to treat this like a trade secret. Has anyone reverse-engineered their communities? I've been capturing updates but I'd rather not guess-and-hope on a production session. Their routing is stable, but I need more control than "call support and wait three days." Any leads appreciated.

Yes the Documentation is always the Problem with these Providers. I have analyzed the BGPUpdateMessages from InterServer using my LookingGlass and found some interesting Community values:

The Prepend communities seem to use the Pattern InterServerASN:70 to InterServerASN:73 for one to four Prepends. The Blackhole community might be InterServerASN:666 no I am not sure about the last one.

I will check my Packet captures again and report back. The whoisDatabase had no Remarks section unfortunately.