1930 Victoria, BC to Brussels, Belgium, registered airmail with #C1(3) 5c airmail and #154 8c Scroll tied by purple “Victoria Sub Office No. 1 BC” (Aug 16) MOOD cancel on cover. Reverse with Victoria Sub No. 1 MOOD (Aug 16), two strikes, Victoria cds (Aug 16) and Montreal B&F Div (Aug 21).
Airmail rates to Europe were rarely used at this time.
Jan 1, 1928 to July 31, 1928 8c per ounce, 4c per additional ounce
August 1, 1928 to Feb 28, 1930 , 13c per ounce, plus 14c per additional ounce
March 1, 1930 15c per ounce
So this cover appears to have been paid using the former rate in effect from August 1, 1928 to Feb 28, 1930 at 13c per ounce, plus 10c registration for a total of 23c postage paid and allowed.
The rate should have actually been 15c per ounce, plus 10c registration for a total of 25c, as the cover was mailed in August 1930 after the rate went into effect on March 1, 1930.