Door Frame material - 2018 320 Boondock

stepheng

I'm looking at adding a shelf above the rear cabinets in the back of my 320.  I know the shelves over the windows, etc. are Baltic Birch plywood, but what material is used for the door frames and cabinet face frames?  Birch?  Want to use 1 x 2 material on front of shelf to create a 'lip' and stiffen the shelf.