Regardless whether these notes are relatively common or not, sooner or later these are going to take a big jump in pricing again.
I agree completely.
Here, BTW, are the Charlton catalogue values over the years...
Charlton 4th (1991) EF $200 AU $400 Unc $900
Charlton 5th (1992) EF $180 AU $350 Unc $700
Charlton 9th (1996) EF $150 AU $250 Unc $550
Charlton 11th (1998) EF $200 AU $350 Unc $700
Charlton 13th (2000) EF $240 AU $500 Unc $900
Charlton 15th (2002) EF $225 AU $450 Unc $800
Charlton 17th (2004) EF $225 AU $450 Unc $850
Charlton 18th (2005) EF $225 AU $450 Unc $900
Charlton 20th (2007) EF $200 AU $400 Unc $825-900
Charlton 22nd (2009) EF $160 AU $325 Unc $650-725
If you follow the bouncing ball, these test notes are near their all-time low in value, so they will probably go up again soon. So the short-term investment potential is there. Long term investment... not good. If we assume the catalogue values are more or less correct, these notes have not improved over the early 1990s, back when small chartered notes could be had at a couple dollars over face.
Consecutive notes are highly overrated and are used frequently to scam naive buyers who think consecutive = Unc.