I decided to remove my 8" Wifred O. White Constellation compass to inspect the sprocket and chain. Wish I knew now what I didn't know then,...

I removed the screws around the rim and gently pulled the ring. Now I can see I loosened the O ring seal and lost an ounce of fluid. Blast! Repairs and service are still available on these old compasses. The Constellation was designed in 1947. They must have been standard on many boats like mine up until 1961 when Danforth took over the company and put their name on the Constellation compasses. My binnacle is built by Kelvin White Nautical Instruments, the White family business was vibrant in this era.

The compass was working fine, no air, the oil clear, the card is still bright white, not yellowed. The diaphram, O ring all appear working fine(tightened retainer, no leaks), so I'll just refill. These hold 1.25 gallons of oil but I'll attempt to top it off.

It has to be tricky to get all the air out. What about oil? Mineral oil ok? Should I fill it in the walk-in milk cooler at the grocery store?