How one would determine polarity of Altec 808-8G ?

Apparently this Altec speaker (I am not familiar with) is very sensitive to applied DC voltage so proceed cautionsly.

A safe approach involves use an ohmmeter set on the low [R X 1] scale, which was a nominal 1.5 vdc output. The output impedance of the meter helps reduce the applied voltage/current surge to the voicecoil. A 1.5V battery with a flashlight bulb connected in series should also be a safe current limiter if you have no meter, but do buy a at least an inexpensive DVM which is pretty much mandatory for speaker work anyway. Limit the time duration of the applied dc source voltage to only as short a time as necessary.
The aforementioned regarding polarity behavior is accurate.

Thanks for your inputs. I used 3 volts and observed the diaphragm moved forward. It easier to see diaphragm movements if you let the light shinning on the diaphragm at certain angle. I also noted that the metal nut/cap that clamping the speaker cable onto the speaker had an dash stamped on top. It looked like a negative polarity sign but it was on the positive speaker tap.

"I also noted that the metal nut/cap that clamping the speaker cable onto the speaker had an dash stamped on top."
After looking at different Altec HF drivers. I found that the dash was actually a number 1 and the other cap had a number 2 stamped on it. I gathered that number 1 is positive and number 2 is negative.