understanding attachinterrupt in a pulse counter

mechengncl:
if
100 - 0 >= 100 (YES, go ahead - it looped 1000s of times before millis got up to 100 ms)

[....]

put val of count in copyCount ( 0, at the moment)

If the Arduino has been running for 100 millisecs I don't understand your thinking when you assume that the value in the variable count will be zero?

If you explain your thinking it will be easier to help.

...R