What you have is what is known to collectors as a T-series HP, arguably the most desirable of the commercial variants (T series was mfg from roughly 1964-69) as it is considered by many to be the pinnacle of FN quality when it comes to HPs. That time is thought of as the "sweet spot" with regards to fit/finish/QC etc. Red back grips and round hammer are correct and it looks like the bbl has been switched out as noted by Xfuzz nice pistol