Registered just to respond here because I saw some misinformation that I believe needs to be corrected. The RO-oriented reconsideration that is noted in M21-1 comes from 38 CFR 3.156(b). The reason none of you are looking at that is because the actual regulation does not refer to the situation as a "reconsideration." That word is used in that context at the RO in a manner that is very different from how it operates at the Board, and it somewhat misleading to even call it a reconsideration at the RO level. It is simply a situation in which the finality of the RD is vitiated. If you want to know exactly what 3.156(b) does, you should read Beraud v. McDonald, 766 F.3d 1402 (Fed. Cir. 2014).