My question is their any significance of finding same FPN/BPN across different dates/signatures/series of notes.
For the average collector- the answer is "no, there is no real significance finding same FPN/BPN" across different dates/signatures/series. On occasion, notes will have the same FPN/BPN according to a pattern which is explored by mmars in a thread below:
http://www.cdnpapermoney.com/forum/index.php?topic=12013.0 It appears as if all the polymer notes will have the same FPN?BPN as the technology to print these has changed.
For older series:To a veteran collector the pattern of FPN/BPN is of interest because they wish to know more about the printing process. Also- when errors are found sometimes knowing the FPN/BPN patterns can help these collectors predict the occurrence to the error. For example, some BTT & BTU $10 notes had the $20 (queen's head) watermark. knowing the pattern discussed above can help predict where to find other notes that could have the same error.
The other interest re: FPN & BPN is when the BPN goes missing as it did in some 1954 $1.00 regular issue and asterisk replacement (most notably the *B/M). Some Devil's Face notes also have missing BPN.
A pattern of missing BPN also occurs for the $20 BIRDS notes and the BPN colour of some BIRDS $5.00 Series notes were either yellow or blue.
For more recent series:For BIRDs/Journey notes:
More collectors are interested in the notes printing date, signatures and prefixes which will sometimes indicate change-overs, inserts or other factors that make the note less common and more collectible.
