Wildland Fire Fuel Sizing Gauge, also called a "Go, No-Go" gauge used in assessing wild land fire fuel quantity. This design is the same design generally used in the field today, and is based on the USDA FIREMON report:
https://www.fs.usda.gov/rm/pubs_series/rmrs/gtr/rmrs_gtr164.pdf
I have posted two designs:
The author marked this model as their own original creation.