NO2A: "I`m sure in the old days it was much tougher to measure your frequency accurately,even with xtal calibraters vfo`s still drifted."
Measuring exact frequency was a bit more challenging, yes. But being inside the band was easy if you had a calibrator and set it against WWV.
NO2A: "But with today`s stability and digital readout i`m surprised how many times i`ve heard dx working just over the band edges."
You don't know for sure what rigs the DX is using, though.
NO2A: "It`s one thing to be on 7002 khz,with a 500 hz. filter,and another thing to be on 7000.5!"
But if the carrier is on 7000.5 and the keying shape is good (no clicks), the entire signal will be inside the band - and legal.
One trap some hams fall into is not really understanding the limitations of a "digital dial", and what it really tells you.
For example, if a rig's frequency is accurate to, say, 50 parts per million (.005%), that's 500 Hz on 30 meters. Components age - how close is a 10 year old rig, anyway?
More important is the issue of what the dial actually reads. On SSB, it is typical amateur practice for the dial to read the suppressed carrier frequency, and the actual signal extends a couple of kHz above or below that. (Forgetting this is a common way to be outside the band on 'phone).
But on CW, what does the readout mean? The center of the rx passband? The transmitted carrier frequency? The zero-beat frequency? Depends on the rig. There's a 750 Hz error waiting to happen.
Sliding outside the band was and is a way to get away from QRM - and a way to get a pink ticket.
73 de Jim, N2EY