(:Document: N :)

¹ Werner H. Rudowski, “The Schnellkalkulator ‘System Bloch’ ”, The Journal of the Oughtred Society, vol. 14, no. 1, spring 2005, pp. 46–52 (↑)

Very rough dating

On the issue of dating, from the above we can identify that serial numbers 327 and serial number 478 (mentioned by Rudowski) are stamped “DRPa” (Deutsches Reichs-Patent applied for) whereas serial number 1049 (sold by Antikma.de in 2011) is stamped DRP (with the patent now approved).

All subsequent serial numbers including 1144, the present Calculant object (serial number 2178), one owned by Rudowski (serial number 3211) and serial number 3318 are stamped DRP. One designed for the French market (serial number 6197 and sold by Wormel on ebay in June 2012) is clearly much later. One other was sold on ebay in 2008 but details are not yet available.

On the issue of dating, we can identify that serial numbers 327
 and serial number 478 (mentioned by Rudowski) are stamped “DRPa”  (Deutsches Reichs-Patent applied for) whereas serial number 1049 (sold
 by Antikma.de in 2011) is stamped DRP (with the patent now approved). 
 

Known Bloch Schnellkalulators

All subsequent serial numbers including 1144, the present
 Calculant object (serial number 2178), one owned by Rudowski (serial
 number 3211) and serial number 3318 are stamped DRP.  One designed
 for the French market (serial number 6197 and sold by Wormel on ebay
 in June 2012) is clearly much later.  One other was sold on ebay in
 2008 but details are not yet available.  

On the issue of dating, we can identify that serial numbers 327
 and serial number 478 (mentioned by Rudowski) are stamped “DRPa”  (Deutsches Reichs-Patent applied for) whereas serial number 1049 (sold
 by Antikma.de in 2011) is stamped DRP (with the patent now approved). 
  All subsequent serial numbers including 1144, the present
 Calculant object (serial number 2178), one owned by Rudowski (serial
 number 3211) and serial number 3318 are stamped DRP.  One designed
 for the French market (serial number 6197 and sold by Wormel on ebay
 in June 2012) is clearly much later.  One other was sold on ebay in
 2008 but details are not yet available.  

Assuming a reasonably slow startup in demand, assuming that production began when the first patent was applied for (since it cannot be earlier), and knowing that the patent was granted in 1922 gives as a guess the table below which is at best suggestive of a date for this machine (Nr 2178) of around 1924–6