"Charles"
The easiest way to check scope BW is to use an RF generator - any decent one with levelled output will do, long as it goes out to a couple of hundred MHz.
Anecdote:
On more than one occasion, techs have questioned the practice of using a
10MHz or more BW scope to test a piece of electronic audio equipment for flat response from 20Hz to 20kHz and beyond.They asked :
" How do you know your scope has a really flat response ? "
I replied:
" Square waves ( audio frequency understood) look perfect " .
... Phil