K-28 Tender Plate???

I need some expert help here. I am being offered a "Tender Plate" from K-28 # 478. I am very skeptical of it as in all the photographic research that I have done, I have found no number plates on the tenders on the K-28 or any class of NG. The plate is a thin but a cast iron plate with a raised border with rounded inside edges. It measures roughly 18" wide and 10 inches tall. It does appear to have been on some sort of engine at one time as it has grime. The numbers 478 are BRASS and rivited into the plate. Did this engine ever wear anything like this? It is NOT the typical D&RGW cast iron boat anchor type number plate. Any thoughts or advice is appreciated! I would be happy to email a photo if anyone has any ideas.