Does anyone know whether the napkin rings sold by cooksons are hallmarked on the inside or outside please?

I want to make a silver toothfairy 'box' for my neice and would rather it was hallmarked on the inside so that if I feel capable I can etch a design onto it. I've never made anything quite so big before am looking forward to the challenge (shes only 4 months old so i have a few years yet to sweat over it before required!) I'm wondering whether it should be a loose fitted lid or whether it should be hinged lid but having never hinged anythging before I feel this to be a huge job, I've also never etched anything either ... so will have to take on smaller practise projects incorporating hinges and etching in my jewellery.