On 14-Dec-04, at 4:25 PM, Tim O'Connor wrote:

My theory is that it was a simple check digit -- if you saw an

even number on a switchlist or some such document for a coal gondola,

you'd know something was wrong.

That's always been my understanding as well, Ian.

There's only one problem with this theory. The C&NW had some

car series with even numbers only... It seems to me that just

as likely an explanation is that it provided a neat way to

provide for future expansion without introducing a new number

series. I know C&NW did "backfill" this way with a large group

of PS-1's that were interleaved with earlier orders of the

same type of car.

This probably just means C&NW did this for some other reason. Only some of the Canadian roads opted into this odd-even numbering thing --

after mentioning Canadian Northern (with their fleet absorbed into Canadian National during the 1920s) and Canadian Pacific through about 1913, it also occurs to me that the Temiskaming & Northern Ontario (later Ontario Northland) also did this through the 1920s, and the Quebec Central also observed this practice in the first half of the 20th century. They all followed the same even number for a house car, and odd number for an open car practice.

CP also "backfilled" at least one series (295000-series auto cars as I recall) when they discontinued the odd-even numbering practice about 1913 with new odd-number cars interleaved into the existing even-number cars), although other existing series were just left the way they were. New series were numbered consecutively.

The only railroad I've heard of that implemented a reliable

"check digit" scheme is KCS. A check digit is a mathematical

function that takes the other digits as input, such that if

ANY of the other digits is wrong, then the check digit also

will be wrong. (Error detection and even correction is very

common in computers because storage & communication devices

are inherently error prone.)

Somewhere around here I have the KCS check digit formula (which strikes me as very useful if you're modelling a six-digit KCS car), as well as the ACI check sum formula (Iess necessary unless you're modelling ACI labels in a rather large scale!). Of course check sums aren't perfect either, but they do reduce the odds of a mistake considerably.

Ian Cranstone

Osgoode, Ontario, Canada

lamontc@...