First came the Northrop BT. Modifications and refinements (really a wholesale redesign) to the BT became the XBT-2. In the meantime Northrop became the El Segundo division of Douglas and the XBT-2, Bu/No 0627 became the XSBD-1. Be that as it may, the first production orders for the SBD-1 on 8 April 1939, for 57 SBD-1s and 87 SBD-2s. All of the -1s went to the Marines, into VMB-2 and then VMB-1 starting in June 1940. The -2s went to VB6, VS-6 and VB-2. Looks like VB-2 was first, sometime in November 1940. All 87 -2s were delivered by May 1941. In December 1941, SBD-3s went to VS-2, VB-5, VS-5, VB-3 and VS-3.
Rich