Front, lens view
Left: NSPU
Ctr: PN58
Rght: PN51
Note the PN58 & NSPU have a single round front lens cap the dark filter must be on during daylight use, the PN51 uses a different updated filter style.
Ctr: PN58
Rght: PN51
Note the PN58 & NSPU have a single round front lens cap the dark filter must be on during daylight use, the PN51 uses a different updated filter style.
Other Sizes: Original