Without getting one out of stock on Monday a quicker way to check is they should be 1mm steel. As they come out of the same factory, as the others sold in the market already, this stamp may not be a 100% guide. The Rare Spares ones are made to order. Make sure you have a clean edge to measure . It depends on where you bought it and if it was in a Rare Spares carton. I'll check stock regardless.