Whiting Mystery Mark

I have a lovely Violet lettuce fork, the back is clearly marked with the Whiting mark, then the mystery mark which I thought would be a date mark, as Violet was introduced about the same time as the date marks. However, it doesn’t seem to match any of the date marks. As it is a tiny detail I tried to photograph it through my jewelers loop…

Thanks for your help, albeit in advanced.
whiting.jpg