Parker 25

Very nice @Darkbulb...

Check the threads inside the top part of the barrel - if they're brass, then they are pre-1980.

Note the 'arrow clip' as well. Very early 1950s jotters had a plain clip. Still and all, they could be late 1950s onwards and the Jotter remained pretty much unchanged from then into the 1970s...

Are there any date codes stamped on the back?
 

Thanks and will do.
I'll look for date codes as well.
With the bottom one having a domed clicker it should be a rather early one.

 
And, yay, received a black Parker 25 in the mail
This one was said to be new and never used and looking at it I can believe it.
$26 but I think it was worth it. Great looking pen!



Next to my brushed steel one:


I'm afraid that its decades of being ink-free will soon be over as this is a pen I fully intend to use


Finally a nib comparison.
I think the blue (on the left) is a fine nib. Is it possible to tell from this photo what the black one (to the right) is?
 
Parker 25 is a fine pen and its cheap price belies its performance. My favorite fountain pen was the Everharp Skyline. Beautiful to look at and to write with especially the flexible nib ones. Had a Waterman Edison in green, best looking pen I ever had, you could even take it on airplanes without it leaking. Trouble was I just couldn't write well with it as it just didn't suit my hand.
 
I suspect that's a medium nib.