Temuka fish plates - do the numbers mean anything?

Hi there, I have 4 Temuka fish plates and they all have 36 with an 8 in middle circle. I'm assuming it identifies something about it being made and does this add to value having a certain number? I remember my Mum visiting the Temuka factory in the 70's I think and brought some then but I'm not sure if these are those - I thought she got rid of hers so might've come across these in an Op shop and by then knew they were of some value. Thank you.