I've currently got a Burnham B54 and CS no 753 and neither of them will budge. I've re-sacced a few burnhams and 2 Handfuls of Conways and never had 2 pens that after half an hour at the most of tugging won't move.
The burnham likely is a thread section and the Conway is likely press.
I''m hesitant to soak them or heat them as it may cause distortion.
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