...was yesterday, but I didn't get a chance to post this before going to bed.
I won this fountain pen in an online auction. Not my first vintage pen, but the first I bought online.

What happened was: I was bemoaning that while I had a Chenqing pen to go with my WWX notebook, I still didn't have a great pen to match my LWJ notebook. @tunalaq.twitter suggested looking for something that echoed the look of his guqin, to follow the theme, so I typed in "pinstripe fountain pen" to see what would come up. This...obviously isn't what I was going for, but I thought it was really neat.
Arnold pens were apparently the cheap knockoff of their day, so I wasn't expecting anything in perfect condition. Almost surprisingly, the sac appears to be intact. But the feed doesn't really work--it doesn't bring the ink to the nib. The nib itself is great, though! It's a flex nib, and I've been wanting to have one of those for a while, and so far, it seems to work fine in my Moonman pen. I'd be pretty happy with this purchase if the nib was the only thing I got out of it.

But I'm not going to stop there--look at this:

Those two sections look the same size...I wonder if I could make a frankenpen?