It's obviously a level of some kind.
The ends that curve downward are still common on the European cast aluminum levels made companies like Stabila, although Stabila doesn’t sell the longer versions in the USA.
The letters being imprecise could simply be from how the mold was made, especially if the item was low volume.
Cast iron was certainly used for levels at some point, and still is by Starrett.
Maybe it was made for setting up machinery or other karge structures, were the precision of a machinist level wasn’t needed, but were level to the accuracy of a carpenter’s level was.
The weight of the cast iron would help keep the level in place in case of vibration, or movement in the case of adjustment to a large wood beam.
