Motley was never a Ram. Always a Brown.
Actually that's Kenny Washington in 1948. When Washington left the next year, Tank got the number 13. In 1952 when all teams went to traditional position numbers he switched to 35. That's also when Van Brocklin went from #25 to #11.
The Rams had leather helmets (in that pic) when Gehrke first painted the horns on. Next year (1949) they went to red and yellow and switched to plastic helmets before going back to blue and yellow from 1950-beyond.