12DW7 - 7247 - ECC832
The 12DW7 is a fairly obscure tube that several amplifier manufacturers used in the past. The tube is essentially one-half 12AX7 and one half 12AU7 with unbalanced triodes. It makes a lot of sense to use in circuits with limited space.
Compatible and/or equivalent tubes: 12DW7, 7247, ECC832.