It is a correct Budd dome.
Nope, Lionel's dome is not even correct to represent the dome pictured, which is an ex-D&RGW car. The Rio Grande car has curved glass on the lower windows and Lionel's has flat glass. Also notice the D&RGW's dome windows are angled forward slightly.Ken
I figured there was more history to the Rio Grande domes, but I didn't have access to my books at the time.