The 20 series is the smallest
of Conklin's Crescent Filler pens. The 25P is the
"pocket" or short version of this series, and the 5 digit
probably indicates that it is a slim version, sort of like Waterman's 52
1/2V.
The first three pictures below show this 25P as it was when I got
it. The cap and barrel were badly oxidized on one side, but still
black on the other, plus there were a pair of black stripes, one around
the cap and one around the barrel. I think this pen may have been
displayed with elastic bands around it and left in one position for
quite some time. The #2 Toledo nib was quite dirty, and the ink
sac was completely hardened.
A gentle application of heat helped to loosen the section from the
barrel, and the old ink sac came out in one piece. I drove the
nib/feed out of the section and treated them to the ultrasonic cleaner
plus some extra cleaning. At some point in their past, someone has
tried to do something to the nib/feed with pliers, and there are some
permanent marks right on the wings of the nib and on the edges of the
feed, but these seem to have no impact on their functionality.