Hi Rmanz,
At a first quick glance this one should be a 1162/173 Omega bracelet and was fitted to (for instance) the Seamaster 300F Hummer Diver (Ref. 198.0016), the SM Chrono Ref. 145.0014 or the Mark II (145.0034) back in the early 70th.
Not original for the Speedy since there would be at least 633ish endlinks have been installed. Same with the 1162ish reference for the bracelet itself, there should be a 1171 bracelet in place instead (pending on the YOB).
Could you show a picture of the hallmark inside and from the Omega logo outside the clasp?
Cheers,
Winny