Should a 1978 Submariner still glow at night?

[datejustjohn]

Well my brother has a 1978 Submariner 1680 with original dial.
When he purchased the watch it was represented as being original and not having been restored.

After wearing it all day the markers and hands glow rather brightly at night. Why would that occur? We are thinking it may have been relumed. It looks original enough to us. He also has an 81 Submariner 16800 which does not glow at all, not even a little.

Is it possible that light is still exciting the lume on the original dial after all these years?