Identification of Baby Spoon & Fork

I’m wondering if someone can help identify the metal and marking on this baby spoon and fork. These belonged to my mother. Since she was born in England in 1921, they could be British and could be nearing antique age. I’m assuming they’re silver but could be wrong. The one that hasn’t been cleaned has an unusual colour to it.

I’ve tried to clean up the fork in the top photo a bit. The spoon has been left untouched. As you can see, they’re 4 inches long.

There are no markings that are typical for silver. The only marking on the back is difficult to read. It might be 5LT or SLT? Turning it the other way around, it appears to read possibly as 175. I’ve spent hours online trying to source this set and identify the marking but without success. Is anyone able to shed some light on it for me?

Thanks so much!