HBAL is generic for high altitude balloon. Loon had registration numbers that ended with an LB for Loon Balloon as in N253LB. When Loon closed in 2021 Raven Aerostar took over the majority of its equipment. They were re-registered with a TH at the end for ThunderHead. They have many balloons currently registered as
N251TH, N252TH, N253TH.
N254TH, N255TH, N256TH,
N257TH, N258TH, N259TH,
N870TH, N871TH, N872TH,
N873TH, N874TH, N875TH,
N877TH, N878TH, N879TH,
N930TH N933TH, N934TH,
N936TH, N937TH, N938TH
and N939TH.
Here is some of what they do: https://youtu.be/GPVivHixhTk?feature=shared