I have been collecting Bank of Canada series for 40 & have no idea what sort of premium would go with your DC-18a (P-27a) $1.00 from 1911. It is a 2 digit radar & I like it but I'm not sure I'd be willing to pay a premium for such a cool serial #. My reason is b/c I'd want it either "original" BCS or "EPQ" from PMG since so many DoC notes were pressed (& these are rarer & more significant in my mind).
If you have a Charlton, you will know that the guide doesn't have good estimates for radars from 1937 & prior. There are many collectors who pay a substantial premium for radars of the 1935/37 & even the 1954 Devil's Face series. But the BoC are collected by a wide collector base (including world collectors). The premiums paid are usually highest (& sometimes crazy) for the higher EPQ or "Original" certified examples.
If you got vague or mild response from other forum collectors it is likely that collectors haven't had much exposure to special numbers that far back. I wouldn't be put off by that: its just people don't know & some will make comments about the # (odds) of radars. While it is true that 3 series were printed for the first series (yours) & another 4 series for DC18b, and 8 more series (DC18c/d), there are greater chances of other radars. But that's beside the point. I don't think that's the issue when it comes to a premium paid for a note like yours. It would probably be more about the older generation collector (who may be less willing to seek radars) & who may prioritize condition whereas the younger generation collector may prioritize special numbers. If the Dominion notes were cheaper (& there were far more collectors looking for special numbers), I'm sure more collectors would be providing you with feedback & more willing to pay a premium. The only way to determine what the premium would be would require you to put if up for auction (or find an auction result for a similar note).
Does that make sense?