At first glance, it may appear that all enclosures in the MCD series from Hoffman have a mounting plate included. The datasheet on the product display page for 1441-MCD18126PER5-ND does indicate the following:
Generic Statements May Not Apply to All Parts
I do think this would be considered a generic statement for the series. This datasheet appears to be a catalog/series datasheet that contains several variations. In this instance, you do have to check nVent - Hoffman’s site for detail:
This page does indicate that the mounting plate is not included for this specific part.