If you haven’t read it already in my twitter updates, I purchased a Hero 329–a replica of the infamous Parker 51.  And however this pen doesn’t fill in the same way as some of the Parker 51’s, this is a very commmon filling mechanism.  This is for use with fountain pens with ink bladders.

It’s of note that during the video I tap on the bladder just after disassembling the pen-and this is where you have to press the compress the bladder and release the ink.  

1. After releasing the ink back into the ink well (or elsewhere for disposal)
2. Dip the nib into the inkwell, release the bladder.  This will draw fresh ink into the bladder.  
3. Repeat the last two steps to ensure there is no dried up ink or contaminants in the pen (optional).