Buckley Handle Cylinder

[goodolddays]

Hello, I have a 10 cent buckley slot machine and I am in need of tips for repairing the small brass cylinder that is supposed to dampen the return of the handle. Currently the handle just slaps back after being pulled unless you hang onto it and manually return it.
This is what I have tried so far, I unsolidiered one end and found that there was a small piece of gasket material which was worn and that the cylinder was out of oil. So I replaced the gasket piece with rubber of appropriate thickness, put some hydraulic oil in the cylinder, and resolidiered it. The handle worked properly for a while, but now it has quit working again.
Should I use leather or gasket material instead? Also, What type of oil os best to use in these small cylinders?
Thanks for any help anyone can offer!

[goodolddays]

Here are some photos of the cylinder and machine in question. I ended up taking it apart and putting another piece of inner tube rubber in it with hydraulic fluid for the oil. This time, I reversed the rubber so it faces the back of the cylinder, the pump now works well and I would call the second attempt a success.