Assertion: fountain pen's ink | /r/ObjectUse | used in the 51
Facets:
Source sentences:
text: Parker was careful to print prominent warnings on caps, labels, and boxes that the ink could only be used in the '51'.
text: Parker was careful to print prominent warnings on caps, labels, and boxes that the ink could only be used in the 51 (and, later, its economy version, the 21), and would damage any other pen.