Outside chance that maybe the top one could be an 83 instead of 73? I cant recall the early 70s Hi-Speeds exactly but know I've seen darker earlier ones myself.
I've found that SOME earlier ones had smaller throats on the grip and know I have seen the "3" start of the serial number start over the next decade.
Only a guess but if I had them in my hand I would assume at first glance the top one is from quite a bit later than the bottom, but could easily be wrong...... also NOT a howatt expert yet have seen quite a few and owned a half dozen.
You should see the thin throat and FRAGILE, dinky, thin limb tips on my 1961 Hi-Speed.
again, just a guess going by what Ive seen.
Nice bows, regardless.
God bless.