"The licence is issued
with a ‘T’ (reference) number rather than a vessel call
sign; therefore the vessel name is usually used as an
identifier. The T (reference) number is not a call sign
recognised internationally and licensing details are not
sent to the ITU."
With lots of other useful info too.
Do also consider that if it's a DSC handheld then it will have a unique MMSI number - or at least, if you have more than one with the same MMSI running it will get unreliable and potentially unsafe in an emergency.
Hope this helps