SOLVED How to identify who intialized timer1 interrupt?

I would like to identify who ( which code) initialized timer1 interrupt.
I could vary the actual time somewhat, the accuracy is not that important, and have the ISR read the TCNT1.
Or setup an input port pattern on initialization and read that in ISR.

I am open to any other reasonable and to the subject suggestions.
Thanks for you time and help.

Solution - use global variable as timer1 state.

Vaclav:
I would like to identify who ( which code) initialized timer1 interrupt.

In the context of your question, there is not any code that initializes any interrupts associated with timer 1.