Pea & Mange Tout conundrum...

Ok, so it's a rookie mistake, but after carefully labelling all my different varieties of peas/mangetout, somehow the 'indelible' marker I used has become 'delible' and each of my peas is now marked with a helpful empty white stick!

Is there any way of telling the difference between mangetout and peas proper? There's a very big risk that I'm happily chomping my way through my peas as mangetout instead!!