The A.D. 8882B revisited

More on my AD8882B (pictured above and left)

Unlike modern electronic equipment, where many components are date-stamped, it is virtually impossible to estimate the age of an R1155. The serial number will give some clues, but apart from that, there is little to shed light on the exact date of manufacture. This is the question that has been nagging me regards the age of my AD8882B ... I know that after WW2, for installation in commercial aircraft, the R1155 was modified and it reverted to its Marconi Type Number of A.D. 8882B. I recently came across a Marconi museum listing which confirmed that the ‘pre-development model’ for the R1155 was definitely designated the AD8882B. Note that the example on that website shows an AD8882B with the earlier Type-13 tuning mechanism but without the vernier scale. Note also that the ‘Instrument Number’ is 6004.Then see this page here which shows and describes a pair of AD8882Bs in a Shorts Solent Flying Boat, circa 1947. Note that both receivers in the photograph have the later Type-35 tuning mechanism. It would be illogical to revert to the older, less reliable, and harder to operate Type-13 mechanism simply because the installation was commercial. I have also found an article detailing the two types of tuning mechanism (Types-13 & 35) which provides a crucial and final piece to the puzzle. As well as confirming that the Type-35 mechanism was fitted from 1942, the article also revealed that the vernier scale behind the fine tune knob was only fitted to early R1155s. It was later omitted, (possibly as early as 1941) since it was inaccurate, due to the fact that the reduction was only approximately 100:1. This more or less confirms that my AD8882B is very likely from around early 1940, adding weight to the likelyhood that it is a prototype and as a result rather rare! Note that the ‘Instrument Number of my AD8882B is 6245. I do not believe that Marconi made over six thousand receivers before the Air Ministry issued the Type Number R1155. It is highly likely that ALL pre-development models bore a 4-figure Instrument Number beginning with 6.   

Receiver Type A.D. 8882B, Instrument Number 6245