This is what it is:
A combination of grease, shellac and beeswax with copper sulfate added as a corrosion inhibitor. It is initially heated and thinned with alcohol during the mixing state, then is allowed to cool and set up."
Petrolatum, Petrolatum, (commonly called Vaseline, Cosmoline, Petroleum Ointment, etc.),â??is a mixture of hydrocarbons, chiefly of the marsh-gas series, obtained from petroleum by distilling off the lighter portions and purifying the residue. It is insoluble in water, soluble in boiling alcohol, ether, chloroform, oils, etc., and is official in three forms, viz.:â??
Petrolatum Liquidum, Liquid Petrolatum.
Petrolatum Molle, Soft Petrolatum,â??melts at 104�°-113�° F.
Petrolatum Spissum, Hard Petrolatum,â??melts at 113�°-125�° F.
The presence of cosmoline is only an indication of long term storage. An unissued military gun dipped in cosmoline would be the same upon removal of the stuff, same as a well used firearm.
Its presence is no indicator of collectibility, only preservation.
Old cosmoline will be very hard and caked on, sort of a redish black color. Fresh cosmoline will be lighter and more of a grease like consistency, considering when used its in a liquid form into which the entire firearm is dipped. Cosmoline is for long term storage, years and years. Since its a petroleum distillate it is not the best for plastic. It won't hurt a rifle stock but would be rough on something thin like Luger grips. Other than getting it off there doesn't seem to be a down side.
Here's a link to what I thought was excellent advice on "long term" storage.
http://www.logicsouth.com/~lcoble/stuff/gunstor.txt
rk