Such toys represent markers in the history of time and recapture the past better than the actual objects they imitate. If you are new to toy collecting our strongest advice is for you not to attempt to clean up the toys you unearth.
Finishes become delicate with age and can be rubbed off or damaged by inexpert handling.
Of all the factors that help determine the value of a given toy condition is right on top. The toy rarity probably would be the first, but condition follows right on its heels. Toys in mint condition do command prices far above that of toys in average condition. Any restoration that might be desirable is best left to experts. Toys in their original boxes sell for a premium price.