Where defendant agreed to pay plaintiff for his services one-half of the proceeds of the sale of two mining claims, but in the sale of these, with others, the interests are not separately valued, the plaintiff is entitled to recover one-half of the entire proceeds of the sale, if it is impossible to determine what proportion should be credited to the claims in which he is interested. Buff v. Hardwick, 19 Colo. App. 416, 75 P. 593. Compare Sec. 493.