G & N Numbers

[dharding]

Hi
Could anyone tell me if the G (Group) & N (Number) markings, were only used on WW1 props
Thanks

[Dave]

I don't know for sure but I think they were used for some time after WW1, but I'm not sure how long after. I'm still not even sure exactly what they mean, except that I think they are production numbers similar to serial numbers.