Here I found another mention of the introduction of the .400 Whelen in February 1st 1923 edition of arms and man hosted on https://www.hathitrust.org

The .400 Whelen rifle is a very high grade weapon
of high power, made for those who desire the very
best, regardless of expense. It is made by hand and
costs $450.00, complete with ammunition, cases, re
loading and cleaning tools, etc. No circular regarding it
has been issued, only a brief announcement.
The entire output for the next year has already
been engaged


Interestingly $450 in 1923 inflation adjusted is just about $6600 Today.

Last edited by 375whelenIMP; 05/06/19 02:33 PM.