: Please forgive what may be a stupid question. Is the Heuer IFR
: timer mechanically the same as the Monte Carlo? Do they have the
: same functions and inner workings? And finally, is the large
: white number dial for minutes or hours? Any info is much
: appreciated.

Your question is not stupid. We each know about different things.

The IFR is a variation on the Monte Carlo Valjoux 7714 movement. So the inner workings must differ in their gearing.
Some later plastic cased pieces have high-beat 7714 movements.
In the IFR, the 'moving window', white number, shows 1-12 minutes, rather than hours as in the Monte Carlo.

The initials IFR stand for 'Instrument Flight Rules' where an aircraft cannot rely on visual surroundings (VFR) during a flight. For example, during poor weather or darkness.
The IFR is part of three instruments needed, the others being a compass and altimeter. (Time, direction, height).
Wikipedia will show a fuller explanation.

There are also some earlier IFRs, without a moving window, showing 10 minutes. I think these may have A.Schild movements. Again contemporary with the earlier Monte Carlo.

I hope this helps
Regards. David