Opinion by
Henderson, J.,The defendant sold to one of the plaintiffs 1,500 shares *218and to the other, 500 shares of stock in a copper mine. Some time afterward, having learned that the plaintiffs were very much dissatisfied with the investment, the defendants wrote a letter to one of the plaintiffs in which reference was made to the stock and to the plaintiffs’ dissatisfaction with the purchase and containing the following: “We, therefore, agree that you shall consider this letter as an option to sell to us, at the end of one year from this date, the amount of stock in Arizona Central above mentioned, which represents an investment on the part of D. B. Lucas of $750, and of Robert G. Lucas of $250, and accumulated interest on each of said items, at this price. That is to say: at the end of one year from this date if you desire to dispose of this stock, we agree to accept it at that time and to pay you the price of fifty cents per share with interest thereon from the date of your purchase.” Within the time fixed in the letter, the plaintiffs tendered the stock to the defendants but the tender was refused, whereupon this action was brought to recover the price fixed. Three objections are made in the affidavit of defense to the right to maintain the suit: (1) the agreement was without CQnsideration; (2) there was a misjoinder of plaintiffs, as they had no joint interest in the subject-matter of the suit and therefore no joint right of action; (3) the alleged contract price of the stock was not the legal measure of damages.
That, the defendants’ letter was an offer of purchase cannot- be disputed. It was the tender of an option to the plaintiffs to sell to the defendants the stock at a stipulated price within a limited time. This offer did not constitute an agreement, but was a proposal to enter into an agreement on condition. Up to the time of the acceptance by .the plaintiffs there was neither consideration nor contract. The consideration of the promise was executory and it was to become a binding contract at the pleásure of the plaintiffs. When the .acceptance of the offer was made in the tender of the *219stock the promise which was conditional became binding in the form of a contract the consideration of which was the mutual promises—the defendants to buy and the plaintiffs to sell. The tender might have been withdrawn at any time before acceptance, but after such acceptance the agreement was mutual and on a legal consideration: Morrow v. Waltz, 18 Pa. 118; Corson v. Mulvany, 49 Pa. 88; 9 Cyc. 283. The case cited by the appellants, Martin’s Est., 131 Pa. 638, as an authority to the contrary is based on a very different state of facts from that presented in the record before us. There was no option given or assumed by the decedent nor any promise on his part to pay for the stock. It was sent by the plaintiff to the testator with the direction to sell it promptly and deposit the proceeds to the credit of the owner. The testator acknowledged the receipt of the certificate and added in the letter: "Whether the stock is sold or not give yourself no uneasiness as to fire or otherwise. I will see that Robert makes you whole.” The claim was based on this promise which was rather the guaranty of the conduct of the son, Robert, than a promise to buy stock, and it is manifest that no contract obligation existed between the son and the claimant. The testator was not bound to buy the stock and the owner was not bound to sell it. There was no loss or benefit moving either way. The promise sued on therefore lacked consideration and mutuality of obligation. '
If a contract existed it was entire and included both of the plaintiffs. The subject of the contract was 2,000 shares of stock for which the defendants were to pay fifty cents a share. The offer was intended to cover the whole transaction relating to the purchase of shares in the company by the plaintiffs and they were jointly interested therefore in the purchase money. A tender of all the shares was a condition precedent to the right to recover, and this could only be done by the joint action of the plaintiffs. We see no difficulty, therefore,. *220in supporting the action by the single contract covering all the shares. The promise should be treated as being made to both of the owners of these shares and the action should be for the price of all of them.
The measure of damages was the difference between the market price of the stock at the time of the breach and the contract price. It is averred in the declaration that at the time the action accrued the stock had no market value and that it now has no market valué and is worthless. The affidavit admits that the stock, is not listed on any public stock exchange and that the deponent has no knowledge of sales of the stock at or near the time of the alleged default on the part of the defendants and is therefore unable to say what the market value of the stock may be. There is a denial that it is without any value whatsoever, but no attempt is made to fix a value or to state any facts from which any inference of value could be derived. The affidavit in this respect is vague and evasive and therefore insufficient.
The judgment of the court below is supported by authority and is affirmed.