Checking the oil-level in an adding listing machine

An old Remington Portable adding listing machine (or Monarch, Torpedo or Dalton) may actually need its oil level checked. Like most mechanical lever-operated adding machines, the Portable has a dampener to control the return-stroke and prevent the machine's lever from 'snapping back'.

The dampener is the metal 'pot' visible at the back of the mechanism on the right-hand side.

The metal 'pot' contains oil, the damper-rod rotates a vane inside the pot against this oil (and a baffle) to regulate (dampen) the speed of the machine. After 80+ years, it may be that the oil-level inside the dampener is low - oil may have escaped (evaporated) via any small gap, e.g. the fit of the rod in the pot. When the vane is rotating in air instead of oil, it of course doesn't work as intended.

The dampener is fortunately designed to be topped-up. It has a filling-plug!

The screw on top of the top is the filling-plug - allowing a check on the oil-level (insert pin, dipstick) and for re-filling the dampener. This machine 'snapped back' with alarming speed, perhaps risking damage to the mechanism. The oil-level in the dampener was indeed low, perhaps half full. 

To re-fill the pot, new oil was inserted with a syringe.

After re-filling the dampener this Dalton (or Remington, Monarch, Torpedo) Portable adding machine no longer snaps the lever back when you let go on the return-stroke. It still returns quickly, but now controlled with an even speed to the rest-position - as designed.

Not an obvious thing to check and uncommon on e.g. typewriters; when an old mechanical adding machine's handle snaps back very fast and hits the end with a clear 'impact', it probably needs its oil-level checked :-)