On 29-Dec-06, at 2:23 PM, Anthony Thompson wrote:

The ARA (later AAR) class designation "HK" appears to have been
introduced between 1923 (when it is not listed) and 1929, when it is
present. Can anyone help to narrow down the time of that introduction?
TIA.

The HK designation was added with the ARA revision effective March 1, 1929 according to the section at the back of the February 1929 ORER. Referring to the same section in the December 1928 ORER (revision of March 1, 1928) does not show the HK class.

Ian Cranstone
Osgoode, Ontario, Canada
lamontc@...
http://freightcars.nakina.net
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