Barry,
* I agree: what you state certainly makes sense.
* I can confirm what is written: Mr. Gibson's Pg. 28 explicitly states "B" scale & the leading "B-xx" of the numerous values recorded make a typo unlikely. Also, note, these are frame values. Maybe only Randall can indicate whether something slipped past the proof readers here.
* Reading further, Pg.33-same Ref. states: While Krieghoff frames average 32 on the B scale, the corresponding receivers averaged a substantially harder 47. The receivers of the other manufacturers tested were correspondingly harder than their respective frames. This hardness difference.....not surprising.....receivers being much more highly stressed during firing than the frames.
* 47 Rb still comes no where close to the 25 Rc (about 100 Rb) which seems to make more sense.
* If any analog to the Mauser M98k receiver can offer insight, Jerry Kuhnhausen, Pg 70-71 of his book Mauser Bolt Actions & Frank de Hass, Pg. 38-39 in Bolt Action Rifles both make good reading on receiver hardness/composition. Essentially, 25-26 Rc case hardness over a 18-20 Rc core. Similar to U.S.'s 1035/1036 steels. However, again, higher 8x57 rifle pressures(48-52k??) vs 30-32k psi for the 9mm.
* Relative to Thor's original observation, this S/N 1161 "K" is fairly early in the start up cycle. I certainly have no documentation of what transpired. However, like a number of manufacturing acceleration programs, I'd hypothesize Mauser's zeal to ramp up on their newly awarded P.08 Military contract got a frenzy going with a number of new trainee's @ Oberndorf. Easy to believe a batch of parts got left in the carburizing box a tad bit long. Of course "Fritz" could have just taken a long lunch. Anyway...no facts; but, the P.08's Mfg. uniformity/consistency seems to have stabilized after 1935 out through 1942.
WR
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