I'm planning a letterboxing trip through eastern NM (hopefully sometime this fall). I have many plants planned. The stamps are almost all carved and I'm finally ready to start placing everything into containers, but I have no idea what containers to use. What types of containers work well in NM and what kind really do not?

Depends on what part of New Mexico. In the southern parts, like in southern Arizona, the wings on locknlocks will fail fall off due to extreme dry heat. Peanuts butter jars seem to hold p well