Hi suchAnight.
Unfortunately, most state highways in the country do not have a numerical value as it is the case of this one.
This "Carretera Paso del Toro - Laguna de San Julián" is a Federal/State highway being a federal highway all the way until it crosses with "Carretera Veracrúz - Xalapa" where most of the traffic is supposed to deroute and transitioning to a state highway the rest of the way for more "local" traffic.
Although signals still say is the MEX 180 officially it is not.
Actually this specific highway is officially registered as MEX-VER without a number, it is a direct continuation of the MEX 180 and road signals treat it as the MEX 180 so I was unsure about changing the tag all the way.