The last time I went to D.C. the American History Museum was still being remodeled and only part of it was reopened. The firearms section wasn't open.
Over a decade ago they had Stancliffe's rifle on display but incorrectly attributed him to Berdan's Sharp Shooters. I corrected them and included some information on him (I dug out his service record and pension application) as well as his image.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!