concurring:
I write separately simply to state that I do not believe that Butler v. Derwinski, 960 F.2d 139 (Fed.Cir.1992) spoke to equitable estoppel, a distinct doctrine. In my opinion, Irwin v. Veterans Administration, 498 U.S. 89, 111 S.Ct. 453, 112 L.Ed.2d 435 (1990), is still controlling law in this field.