The German built 400 Slants are not easy to date because factory records were ‘lost’ I believe. Online info is scarce & so I have been accumulating SN details for these machines & I have a couple that came with the purchase documents, which help to narrow down the date of manufacture.
The Serial Numbers are sequential, starting in 1954 (Karlsruhe) for the 215, 216, 218 models. The start date for the 401 is not certain for me, but looks to be late 1959. Talking about the PAxxxxxx SNs which changed to PBxxxxxx close to late 1962/early 63. I have a 431G, PB289117, with its date of sale in November 1963. Latest dates for the 400 series appear to be 1965 which is a relatively small window of 6 years or so.
My list of 20 or so machines, in Serial Number order plus a couple of known purchase dates do help to narrow down the dates of manufacture.
401G PA537828 196?
401G PA597627 196?
404G PA666460 196?
401G PA823616 1962?
402G PB080000 196? On Etsy currently by Greek ‘restorers’ 3FTERS
421G PB167504 1963 JRG on VSS Manual 11/62
421G PB169152 1963? Ians machine
412G PB280731 1963? ToolFool.org
431G PB289117 1963 Bill of Sale 14/11/63 £99 15s
431G PB296469 1964 Bill of Sale 11/09/64 £96 15s
431G PB296978 1964
411G PB356418 1964? Switchable Treadle Electric
431G PB439892 1964
411G PB476653 1964
411G PB538526 1965 Treadle Dated in cabinet 26 March 1965
411G PB608144 1965
This is a work in progress & more verifiable information would help to improve accuracy.
411M MA038602 1964 Italian made machines have a different numbering system.
Manuals dating helps for earliest machines. All below (except 421) in my possession.
401 Manual dated 1959.
411 x2 dated 1963
411 dated 1964
421 dated 11/1963
431 Convertible dated 1963 (No 1)