An ID feature is the triangular brace/fin where the tail boom comes off the aft fuselage... the only H-19/S-55s I've seen in pictures without it are YH-19 developmental airframes.
Could be. Any maintenance call within two hours of flight is called a Red Ball and is a priority one. I learned a lot on many a red ball. By the time I left they were being upgraded with three caracal IV INS systems. If one failed preflight that grounded the aircraft. Most aircraft only had one INS and the navigator new how to navigate if it failed.