What not a creel? How very modern of you to use pencils!
As to that tool, when, for example, hardwood is stacked for several years to air dry (remember, minimum 1 year of drying for every inch of thickness, so a 6in thick oak keel for a boat would need 6 plus years in the stack, ideally much longer) it will darken, weather and probably develop shakes so any pencil or crayon markings will simply fade whereas a carved number, batch or date won't. The modern way is to staple or nail a coloured plastic tag to the end of the timber which is ugly, if functional. Softwood isn't stacked in the same way for years andctends to get used quite quickly so the standard methods of screen printing, branding or even dot matrix printing (or a pencil or timber crayon for that matter) will often suffice