British path racers.
1949 Rotrax "Shirley."


1952 R.O. Harrison "Madison".

Both the Rotrax and the Harrison roll on 700x32s, and feel fine on gravel hard pack. I wouldn't take them mountain biking, but no mountain bike can also legally do time in a velodrome. These were serious machines for road, grass track, packed dirt "path" (ovals), and velodrome racing. One bike to rule them all.

And as stated by another member, one of the ultimate "gravel" bikes was/are the TI (Raleigh and it's subsidiaries) Sports models. These were go-everywhere bikes of their time and with a pair of decent tyres (tires), they are perfectly serviceable. Add a drop bar and ride it until your legs fall off. With air and oil, the bike will probably outlast the rider. Remember, the widespread use of automobiles is a post-WWII change and paved roads followed, so nearly all bicycles prior to about 1960, as mentioned, which weren't solely built and tyred for a wooden track velodrome were made to ride everywhere.
I'll also add anything ridden in the first few Tours de France was literally a go anywhere bike.
Even the ordinary (penny farthing) was ridden all over the world, wherever the rider wanted to go.
Phil