Arcturus 39/44
AC/DC Remote Cut-Off Pentode
1933

The 39/44 was a replacement for the earlier types 139A and 44. These two types had similar characteristics, and the 39/44 had specs the same as the 44. This tube is unique amoung the early Arcturus types as it is the only one known to have used used a (dark) blue bakelite base. However, not all 39/44 tubes have this blue base.