I don't believe, however, that this special numbering was applied anytime during the 1800s. This distinction, then, is important because we should not conclude that since there are full grands with the expected 6-digit number that there was no 'concert grand' series, or vice versa. Thus one might find a Scale 131, for example, with the expected 6-digit serial number and another Scale 131 with an obscure number. This really makes sense, however, only if we differentiate between 'full grands' and 'concert grands.' The former and the latter can be the same model (the Scale 131, for example). So I've reluctantly joined the camp that surmises that there was a separate set of numbers, or at the very least, a very abstruse numbering system for some full grands.
Nor do they appear to be in a year/model, or vice versa, format. On the few I've seen, the number doesn't make sense as the trailing digits of a 1xx,xxx number with the first one or two numbers suppressed.
Unlike the ever-misleading case number, this number appears in exactly the size and spot that a serial number should. in the hundred thousands) with only a 4- or 5-digit number.
I have seen full grands made well after 1900 (whose serial number should be six digits, i.e. I have always been under the impression that Chickering had a separate set of serial numbers for concert grands.
