Armstrong Heritage Flute Serial Numbers

I am at a crossroads with my Armstrong Heritage flute ~1975.
It has the cursive Armstrong script with the block letters below and serial number H-3529. It has french pointed arms on the non-open holes of the body.
I do not see thin wall written on it. I bought this new in 1975. I am not happy with the head joint--it seems stiff in harsh, especially in the high register--seems to need a lot of air and air speed compared to the more silky higher register I have found with my Yamaha 471. I have had trouble finding a new head joint that fits--they are too big. The diameter of the barrel of my Heritage measures 20 mm.
What options do you suggest for a new headjoint that would fit and complement it? I assume trying to sell it 'as is' would fetch ~$500 and an overhaul seems hard to justify..
Also-it plays well--are new pads 'automatically' needed given its age?
Heritage
BY
ARMSTRONG
ELKHART
H-3529

I have a friend who just called me, has a Selmer Flute with case, stamped coin silver made in U.S.A., serial number (or model#?) is 06798. She received this from an older Gentleman's estate, Although nobody is sure, it was mentioned the gentleman had it during the war (world war 2), but this seems speculation. Anybody have an idea of what the possible age/value may be based on the info. provided? Any help would be greatly appreciated, I have not seen the piece as of yet, but plan to do so Sunday. Thanks in advance,
Franz