The Caterpillar 336D Excavator in 1:50th scale was released by Norscot in 2009 with #55241.
Besides the type designation, there are NO differences between the previously released Caterpillar 330D and the new model of the Caterpillar 336D Hydraulic Excavator.
In short, how and why: Caterpillar wants by means of the model number also communicate a better indication of the operational weight of their Hydraulic Excavators: So = 3 series and 36 is +/- 36 tons.