It looks like the plate is made from cast aluminium. I have made a small scratch on the back, this is pictured.
1952 Vintage Cast Railway Wagon Plate Genly Repaired 8-1952
VINTAGE CAST METAL WAGON MAKER'S PLATE. PROCOR WAKEFIELD Circa 1970s
Vintage Cast Railway Locomotive Shed/Bridge Plate? By The Royal Label Factory
1955 Vintage Derby Railway Wagon Plate Genly Repaired M 7- 1955
Rake Of 2 Playcraft P635 Goods Van OO HO Vintage Model Railway Wagon Brown Boxed
VINTAGE CAST IRON RAILWAY SIGN PLAQUE METROPOLITAN CAMMELL CARRIAGE & WAGON 1948
