Looked at amazon reviews, seems included rechargeable batteries haven’t lived up to expectation but are relatively easy to replace
Electrically identical to T600, so all radio performance information of T600 should apply to T503.
Note FRS/GMRS rule changes in 2017 means a license is no longer required to broadcast on “high power” GMRS frequencies so long as the radio broadcasts at 2W or less (which these do). There may still be a note about license requirements in the manual which would indicate they were manufactured before the rule change.
These do not require a license to operate