When compared to the plimsoll symbol used on vessels, the horizontal bar should however extend the boundaries of the circle.
The company used to specialise in making hot water bottles and gym plimsolls.
Inexpensive dime store plimsolls have very thin footbeds (3mm elastomer/rubber outsole, 1mm card, 2mm eva foam) and no heel lift or stiffening.
Plimsolls have not been affected.
Owing to the shortage of rubber, it will be some time before there are sufficient supplies of plimsolls for each child to have his own pair.
Plimsoll demanded safety for those who go down to the sea in ships.
I cannot say whether they always wear plimsolls or sandals.
Then there is our old friend the plimsoll.