On the left side, there is the usual Parker 51 cap shape that I was already familiar with.
On the right, it's a cap that came with a Parker 51 that I recently got from ebay.
It has the 51 printed on it along with "1/10 12K GF" then "Made in USA". However it's suspicious to me that it has a somewhat slimmer apperance, a smaller jewel and a longer arrow clip.
Can the cap on the right side of the picture be legit for the pen it came with? The pen is an otherwise ordinary looking aerometric 51 with the filler that has the black plastic bit at the top and the "To fill press ribbed bar firmly 4 times..." imprint and a barrel that says "Made in England". I think the fact that the barrel comes from England and the cap from the USA is quite suspicious. However, I'm pretty sure I've read about some early aerometric 51s that have a longer clip, so maybe this is just one of those?
What do you guys think?