Here's some information from the web, which is unfortunately not a complete answer to your question. The link below goes to Washington's will, containing a clause regarding a pair of pistols to Lafayette.
Here's a note on the same site regarding the pistols:
"22. Four pairs of pistols were found "in the Study" at Mount Vernon when the inventory of its contents was taken in 1800. The appraisers set a value of $50 on three of the pairs, and $50 on the fourth. The pair of pistols given to Lafayette was exhibited at the Chicago Exhibition in 1893 as one of the "Souvenirs Franco-Américain de La Guerre de Independance." They had been on permanent display in Lafayette's chateau de La Grange. It is possible that these were the pistols that were sent from Philadelphia to General Washington at West Point on 22 Sept. 1779, with these words: "General Washington: accepting of these Pistols will very much oblige Sir Your most obedient very humble Sevt George Geddes." On 30 Sept., in accepting the gift, Washington called them "a pair of very elegant Pistols." By leaving this or another of his pair of pistols to Lafayette, Washington may have been returning the compliment. In 1824 Congressman Charles Fenton Mercer presented Gen. Andrew Jackson with a pair of pistols which, he said, Washington wore during the Revolution and were the gift of Lafayette. Mercer had got the pistols from William Robinson, the son-in-law of Washington's nephew William Augustine Washington. See Prussing, Estate of George Washington, 417-18, Richard and Carol Simpson, "Andrew Jackson's Pistols," (The Gun Report, January 1985), and Andrew Jackson to Edward George Washington Butler, 20 Jan. 1824, in Sam B. Smith, Harriet Chappell, Owsley, et al., eds., The Papers of Andrew Jackson, 5:341-42."
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