I try to incorporate the word "network" into my "net" names. I would see this as "H" + "55" + "network". For me this helps the user to remember the extension. So you don't lose traffic to the com and I also think it adds weight to the "brand". The connotations that come with "network" are very comforting and or reliable.
Take for example in the use of a seniors retirement village. Or a Health Wellness Center. "H" would then be branded in as Health, Home, Heavenly, or something else using the letter "H". The "55" of course would be an age you might target but the "network" aspect is something I would play into my marketing to include an aspect of comfort to potential clients.
A G[][]G search shows a relation, mostly, to a "sony camera" (possible TM issue) and a motherboard ... again a largely produce commercial item with possible Tm issues. So brand it (h55/net) as something other than those two products and services .... and any others that might fall under protected status.
I say this due to the relatively vague and non applicable meaning to the domain name. Your branding efforts would be it's value.
Hydro 55 - 55 gal water reservoir for hydroponics
Hospice Network for 55 and older
Hope this helps .... Good luck
NN