Ah !!!, but .. it is !!I had to hold the weak one almost twice as close to the compass to get the same deflection. It's not very quantitative, but
Assuming *everything else* is the same, and knowing magnetic field (same as sound pressure) decreases with the square of the distance, your 2:1 distance variation implies a 4:1 magnetic strength loss.
As to the Alnico strength loss, if by any chance the magnet was pulled from the frame and then remounted (misaligned / chock full of iron filings?) , you have a huge drop, consistent with what you observed.
If you get it remagnetized, it's as good as new.