Production Run 1921 - 1939
Nameplate      D-1
Serial Number  8Ø365
Manufactured   192Ø
Base size      3" X 6"
     finish    Black Japanned
Damper         L
Ckt Closer     Yes
Aquired        January 2ØØ1
Sold           August 2ØØ2
  to           KG4CYO

Advertised as an Original on a small base in 1921, the Junior wasn't advertized until 1934. Following the logic of the #4 and #6, later known as the #4 Blue Racer and #6 Lighting Bug this key is also called a Martin Junior by many collectors.

The Vibroplex Co. Inc.              William Holly       K1BH
     pg  23 shows a D1 plate dating from 192� with SN 86654
         "It's possible and perhaps even probable that the new logo
         was introduced in October 192�, when the company relocated."
     pg  48 shows a D1 plate dating from 192� to 1936
            Bill shows a C-3 plate from 1918 to 192�
                 and the D-1 plate from 192� to 1936
     pg  49 shows Martin Junior production starting in 1934

Vibroplex Collectors Guide 2nd Ed   Tom French          W1IMQ
     pg   6 shows production from 1921 - 1939
     pg  71 shows production starting in 1921
     pg 1�6 shows a D1 plate starting with sn 79566 in 1921
            Tom  shows a C-3 plate from 1919
                 and the D-1 plate from 1921

Dating Your Vibroplex               John Elwood         WW7P
     SN's 72353 - 8�96� in 192�

     KEY          START DATE/SOURCE             STOP DATE/SOURCE
     Martin       c. Jul/Aug 192�               Oct. 1939
     Junior       WW7P Survey                   "QST", Oct. 1939, Pg. 1�6