The box
A quick info - I have been reading whatever is available on the www about Abel, and I find this interesting passage on the following webpage (http://earlyguitar.net/Abel/Abel.htm):
"At the end of the 1782 season Abel leff London to visit his homeland. He saw his brother in Ludwigslust and probably his younger brother Ernst Heinrich (who was to claim Abel's possessions after his death) in Hamburg. He also spent some time at the court of Friedrich Wilhelm, Crown Prince of Prussia, at Potsdam; Abel had dedicated his op.1 5 quartets to the prince in 1780, and now he was so impressed with his gamba playing that he received 100 louis d'ors and a gold snuff-box. The manuscripts of five of his symphonies were (until 1943) in the Berlin Stadtsschlossbibliothek, which suggests that he composed them for the prince, possibly on this visit. An advertisement in Cramer's Magazin der Musik (25 February 1783) shows that manuscript copies of his sonatas and quartets for the gamba were in circulation."
Unfortunately, the picture is from 1777, which makes it a little early to be Friedrich Wilhelm's. But the snuff-box theory is probably more accurate than the dog-treat box theory. Too bad for the dog.