Firstly, there should be some distinction drawn between sheet numbers and serial numbers. In 1935, the serial number of the note must include the check letter. Without this, it is just the sheet number. Serial numbers uniquely identify a note whereas a sheet number only identifies the sheet that the note came from. In 1935, multiple notes on the same sheet bore the same sheet number but had different check letters (A, B, C, D). Thus, there is not one but FOUR notes with the sheet number A000001. Similarly, there is not 500 notes bearing the numbers A000001 through A000499 but rather 2,000. This is probably why numbers 500-999 are not listed. The numbers below 500 already constitute double the quantity priced for subsequent series.
From 1937 onward, the number on a banknote (including of course the prefix) is unique* and is considered a serial number.
As for valuing 1935 notes with sheet numbers 500-999, I would suggest taking the value for the lower numbered note, then halving that. Of course the final value is always a negotiation between buyer and seller and the word of some schmuck like me or an esteemed catalogue should only be taken as a suggestion.
*I know, I know, there are exceptions such as errors, Lasting Impressions sets, etc. For the purposes of this explanation, disregard those edge cases and focus on the bigger picture.
Logged
BWJM, F.O.N.A.
Life Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
President, IBNS Ontario Chapter.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.