IBM 5155 Manual To Operations page 197

J
This is the Enter key. Its uses are defined by the
programming language or application program you are
using. Refer to the appropriate manual for its specific
function.
When the Print Screen key is pressed with the Shift key,
a copy of the information on the screen is printed.
If
the information consists of alphanumeric characters,
such as a program listing, it will be duplicated on the
printer.
If
the information is a graphic representation,
it can be reproduced only on a printer that supports
graphic printing, such as the ffiM Personal Computer
Graphics Printer.
Keyboard 3-9