The Amateur Archaelogists Hand book for cleaning/preserving Horn/Antler calls for a salt test useing silver nitrate.
Directions say - soak the object in fresh water, remove object & add to the water a drop or 2 of silver nitrate, which may be obtained at any drug store or chemical supply house. If salt is present, the water will become cloudy.
If salt is present let the object soak in fresh water for an hour,then make a second salt test. repeat until a negative result is obtained. (I.E no cloudy water)
Depending on the material your are dealing with, water, alcohol,ether or gasoline are good cleaning agents.
Chart-
Cleaning agents Material
Water ------------------ turtle shell, gold,stone
alcohol ---------------- wood, glass
Acetone--------------- antler,horn,ivory,shell,amber,copper
Gasoline & ether-------grease or simular organic dirts
If the object permits, dip it in the proper cleaning liquid (see chart) until it is covered completely. Otherwise, dip a cotton swab or very solf brush in the liquid and apply.. If you have any doubts about the solution, try it on a small area of the object where damage will not show.. Better still, try it on some less valuable material of the same type.
(Preserving)
The celluloid acetone is the most valuable material known to archaeologists. Celluloid-actetone is unsurpassed for strengthening.!
For Antler - Immerse in celluloid acetone solution until air bubbles stop rising. Remove, dry. Repeat process twice.
For Horn - wash with warm soap & water. Immerse in celluloid acetone solution.
This is probably over kill for your call.! but can likely be applied as a proper cleaning/restoring method.. FWIW, I would likely go a step less + a step further.! To explain, I dont see the need for the silver nitrate test, your call isn't that old.! I would likely just soak the call in water (boiled water)for an hour to remove any salts & then dipp/soak the call in acetone.. I would go a step further by applying a clear satin laquer finish of some type after the acetone dipping.. Hope maybe that will help..