THE GENERAL POST OFFICE (GPO) VT VALVE NUMBERING SYSTEM
Confusing or what, the GPO had their own Valve - Thermionic numbering system comprising of a sequence of numbers in range from VT17 to VT207. Although this alphanumeric code followed the same form as the US Signal Corps one it was quite different. I have produced a look up table that related GPO VT number with UK CV number and commercial equivalent numbers - a first for the internet I think. Enjoy:-
| GPO VT NUMBER | CV NUMBER | COMMERCIAL NUMBER |
| VT19 | CV1612 | VT9B |
| VT24 | CV1636 | LS5 |
| VT25 | CV1637 | LS5 |
| VT26 | CV1600 | CAT1 |
| VT27 | CV1601 | CAR1 |
| VT31 | CV1638 | 4101D |
| VT33 | CV1642 | DER |
| VT34 | CV1614 | ES1500A |
| VT35 | CV1615 | ESU1500 |
| VT36 | CV1602 | CAR4 |
| VT38 | CV1645 | E133 |
| VT40 | CV1647 | LS5B |
| VT46 | CV1616 | 4104A |
| VT47 | CV1603 | 4104B |
| VT50 | CV1050 | HL2K |
| VT52 | CV1025 | DET25 |
| VT54 | CV1618 | ES250M |
| VT56 | CV1648 | 4205B |
| VT57 | CV25 | 4242A |
| VT58 | CV1619 | 4212E |
| VT60 | CV1605 | 4013C |
| VT61A | CV1609 | SW7 |
| VT62 | CV1606 | CAT2 |
| VT65 | CV1649 | E133 |
| VT66 | CV1650 | LS5A |
| VT68 | CV1651 | G445 |
| VT69 | CV1652 | P220A |
| VT74 | CV1654 | L2 |
| VT75 | CV1655 | 4019B |
| VT78 | CV1656 | LS8 |
| VT82 | CV1659 | 4022B |
| VT83 | CV1660 | LS7 |
| VT86 | CV1662 | P215 |
| VT87 | CV1663 | 4021B |
| VT88 | CV1664 | 4022AR |
| VT89 | CV1665 | DH |
| VT90 | CV1732 | ML4 |
| VT91 | CV1038 | MHL4 |
| VT92 | CV1735 | DC2/P |
| VT93 | CV1666 | P610 |
| VT94 | CV1667 | LS5X |
| VT95 | CV1668 | 4033L |
| VT98 | CV1669 | P625 |
| VT100 | CV1040 | PX25 |
| VT105 | CV1673 | HL2 |
| VT106 | CV1674 | AC/52PEN |
| VT107 | CV1675 | N43 |
| VT109 | CV1677 | PX25 |
| VT111 | CV1679 | DA30 |
| VT112 | CV1680 | PM202 |
| VT114 | CV1682 | PENA4 |
| VT115 | CV1683 | MP/PEN |
| VT119 | CV1169 | VMP4G |
| VT120 | CV1688 | 4033L |
| VT125 | CV1689 | PA1 |
| VT126 | CV1690 | 9A1 |
| VT127 | (CV1187) | D41 |
| VT128 | CV1692 | AC/P |
| VT131 | CV1168 | PX4 |
| VT133 | CV1695 | DDL13 |
| VT136 | CV1118 | KT2 |
| VT137 | CV1081 | 4052A |
| VT138 | CV1623 | RG1-125 |
| VT139 | CV399 | MH4 |
| VT140 | CV1166 | LP2 |
| VT143 | CV1696 | PM2BA |
| VT144 | CV1371 | PT6 |
| VT145 | CV243 | 4045A |
| VT146 | CV1625 | RG3-250 |
| VT147 | CV1697 | X41 |
| VT148 | CV1698 | A819 |
| VT150 | CV1699 | SP41 |
| VT150A | CV1700 | SP41 |
| VT151 | CV1701 | XLO |
| VT152 | CV1702 | XP |
| VT153 | CV1703 | XW |
| VT154 | CV1067 | L63 |
| VT161 | CV1710 | 6C6 |
| VT162 | CV1711 | 6B7 |
| VT163 | CV1712 | 42 |
| VT164 | CV1713 | EF8 |
| VT167 | CV1716 | E1541 |
| VT169 | CV1717 | 4307A |
| VT170 | CV1718 | AC/TP |
| VT171 | CV1719 | U22 |
| VT177 | CV1720 | XL 1.5 |
| VT178 | CV1721 | XP 1.5 |
| VT179 | CV1722 | A901 |
| VT180 | CV1053 | EF39 |
| VT181 | CV1052 | EL32 |
| VT182 | CV1723 | V257 |
| VT183 | CV1724 | 5A/102D |
| VT185 | CV245 | 4328D |
| VT188 | CV1727 | SP210 |
| VT189 | CV1128 | GT1C |
| VT190 | CV1728 | WE262B |
| VT191 | CV1628 | GU8 |
| VT193 | CV1100 | KTW62 |
| VT194 | CV587 | DH63 |
| VT195 | CV1863 | 5Z4G |
| VT196 | CV509 | 6V6G |
| VT199 | CV124 | 807 |
| VT200 | CV1065 | SP61 |
| VT201 | CV1056 | EF36 |
| VT202 | CV1054 | EB34 |
| VT203 | CV9 | AL60 |
| VT204 | CV18 | DET19 |
| VT205 | CV1630 | ESP450 |
| VT207 | CV1091 | EF50 |