It appears that the Redskins utilized that site as their training camp in 1941 and 1942, before moving to Balboa Park in San Diego, CA and then to Occidental College in Los Angeles where they remained for many years before returning to the East Coast.
You came close on the year, but the Mark 75 came out for the 57 season, and the Mark 30 on one of the boats was also a 57 model, as shown by its details.
