I'm thinking 1956 on those. According to the catalogs, Snap-on didn't add the high-leverage 7-inch pliers (#387) until 1953. Later, the #387C, which, had no pattern grips. And that logo, despite it looking old and almost hand-engraved, has the hyphen (Snap-on) vs. the short diagonal slash (Snap/on). You could post it on the Snap-on thread and maybe get more eyes on it, including snapmom. She doesn't collect pliers, but might be able to help. The pliers are not always easy to date.