What we know:
Based on patents, new articles, and user research the original 60's formula is expected to contain water, 38% by mass; chlorinated paraffin, 36%; low molecular weight polyethylene glycol, 13%; kerosene 7%; and microcrystalline wax, 6%.
Over the years the formula has changed due to various reasons. One big factor driving change was making the formula safer in case the customer comes in contact with it. IE they broke their lamp and have to clean it up. Carbon tetrachloride, perchloroethylene, and other chlorinated chemicals have been found again and again to be cancer causing with repeated exposure. Due to this liability the formula has been modified again and again to try to remove unsafe chemicals.
Lots of research has happened on these boards where people have discussed reverse engineering the formula.
Original patents for the formula.
What we dont know:
The correct mixtures of the above chemicals.