An old UNUSED speaker in a box for 40 years, wow...
if you are handy, i would replace the Caps with Mundorf with the same value
and might as well replace the resistors too (Dale) and listen.
But as others have recommended. Listen to it First for at least 24 hours and notice if there is distortion or any anomalies in the sound. once that is Good to go, then do the parts replacement.
just my 02cents