I've often seen mt written as the units for metric tons.
There's some ODD behavior where people in the US want to fuck up metric units (MB being the obvious in my lifetime non-engineer renaming of the meaning of a unit). I find the MM of finance confusing (not sure of origin). Calling tonnes, metric "tons", seems to be a US confusing thing. Or spelling metres vs meters.
Or creating units that depend on something country specific like football field (is that FIFA (EU), US, Canadian, Aussie).
Actually it seems common to desire to create industry units: https://www.theregister.com/Design/page/reg-standards-conver...
Sort of a NIH at the county level.
European colleagues regularly go, "what other kind of tonnes are there?" and we get to share the joke of how silly Americans are for still using imperial tonnes.