Being well "over the hill" I am not familiar with a "VFR Stamp." But I do got's an old sea story…..
I used to fly Research and Development flight profiles in an A-4 against the then developing Aegis radar project in Moorestown, New Jersey. To simulate high-speed, low altitude attacks over New Jersey, I had to do these flights in the middle of the night when there was negligible traffic.
With my A-4 pre-positioned at McGuire AFB, this young naval aviator tripped into their flight-ops at 0200 with my VFR flight plan.
They blew a gasket!
Shocked, those AF guys told me I couldn't file VFR. But I told them I was Navy, and could. They said couldn't. I said I had orders. They said no. It was 02:00 in the morning, and AF colonels and Navy Captains were awakened.
Shortly thereafter - and for many nights later without ever another hassle – I launched VFR out of McGuire AFB at 0300, went out over the Atlantic, and then flew many various mission profiles at low altitude and high-speed over the sleeping New Jersyions. It was always to the great dismay of the AF personnel who hated me for operating outside their rules, whenever I showed up at 2AM for another flight.
Good times! All the mid-watch NY Center ATC controllers got to know me, and enjoyed my "performances" which they had rarely seen!