another Plomb 3426, one month off of yours.
The letters don't represent months, Don. They don't go higher than "E" or so, as I recall, during this timeframe. As far as I know, they have not been deciphered.
As long as you brought up the second date code system (4 + unknown letter through 9 + unknown letter = 1934 through 1939), though, I've always thought my set has an interesting spread.
The set, bought together
, from a retired veteran who told me he didn't know when or where he lost the pouch they came in, sure makes you think about a lot more than steel, tools, tappets, and combustion engines.
When it was assembled at the factory by Plomb for sale as a set, it was assembled with a wrench made in 1934, two wrenches made in 1936, two wrenches made 1937, and a wrench made in 1938.
Historically, that actually makes sense. We were just coming out of the Great Depression. From 1934 to early 1937, things were getting a little better. Then there was a sharp downturn in mid-1937, lasting for 13 months through most of 1938, that historians now label a recession. And then things started getting better again, just before WWII.
Point being that it is not at all inconceivable to picture Plomb using new old stock from 1934, 1936, and 1937 - when sales were probably very low - to fill out a set sold in 1938 or perhaps even 1939.
As in many cases, the real value in collecting antique and vintage tools is often in the history going on around them.