Parker 61 pens - These are the replacement models for Parkers successful 51's. The design attempts to improve on the original design. On a Parker 51 the nib, feed, collector, and shell all rotate and must be aligned properly for the ink feed to work correctly. The 61 fixes this by having tabs that align all of these parts for the best results. Another desirable feature at the time was a new filler that allows the filler to fill with ink without having to clean the ink from the front of the pen.  The nib fix was a success but the filler was not. It is not easy to change inks and the pens are not very good at feeding ink to broad nibs. The late models replace the filler with converters and when pens that were sent in for repair Parker replaced the fillers with converters.

Most pens that you find will be clogged with ink. Soaking in water for 3-4 days will usually clear the filler so the pen can be used.