Parker Hale made target sights for many different rifles, the PH16 was available in a number of different models, as listed:
PH16 BSA Sportsman and similar
PH16B ditto, 1/10" higher line of sight
PH16C military Mauser
PH16D Mossberg 42MB
PH16E .22 Mauser with grooves in receiver
PH16F SMLE
PH16J rifles w/flat-side receivers 1.25" wide
PH16K ditto, 1" wide
PH16M Webley & Scott Mk.3 air rifle
PH16N Brno rifles , .22RF & .22 Hornet
The other sight would, at a guess, be for something around .22RF calibre as well.