In Nice Ball Bearing Co. v. Bearing Jobbers, Inc., 205 F.2d 841 (7th Cir. 1953), the parties had entered into a written instrument in the form of a contract for the sale of stock. The appellate court held that evidence of discussions by the parties properly was admitted to show that the writing was intended by them only as a sham and not as an operative contract. No contract was formed because the parties did not intend to enter into a contract, notwithstanding their writing, and expressed that intent to each other. The evidence of the parties' interactions when the writing was signed was not inadmissible parol evidence; it was admissible evidence on the issue of mutual assent/contract formation.