In Bernard Shaw's Arms and the Man, Major Petkoff's old coat is a small domestic object that Shaw turns into an important mechanism of the plot, driving the comedy of concealment towards its resolution.
The coat as means of escape. When the fugitive Swiss officer Bluntschli takes refuge in Raina's bedroom, Raina and her mother Catherine hide him and later smuggle him out of the house disguised in Major Petkoff's old coat. The coat thus becomes the instrument that protects the family secret and links Bluntschli to the Petkoff household after the war.
The hidden photograph. Before Bluntschli leaves, Raina slips her portrait into the pocket of the coat, inscribed to her "Chocolate Cream Soldier." This token is the seed of dramatic irony: it carries the evidence of her secret affection, unknown to her father and to her betrothed Sergius, and it waits inside the returned coat like a small bomb.
The engine of discovery. The comedy tightens around the coat. Catherine insists the coat is safely in the blue closet; Petkoff bets it is not, and the coat is produced, exposing the women's nervous evasions. The presence and eventual discovery of the photograph and the coat force the truth about Bluntschli's night in the house into the open, unravelling the pretences of Raina and Sergius alike.
Resolution of the plot. This exposure collapses the false romance between Raina and Sergius and clears the way for the honest pairing of Raina with Bluntschli and Sergius with Louka. The coat, therefore, is not mere stage decoration but the pivot on which the concealment turns into revelation.
Conclusion. Petkoff's coat is highly significant: as a disguise it enables Bluntschli's escape, as the carrier of the incriminating photograph it preserves and then betrays the secret, and as the object of comic dispute it precipitates the discoveries that resolve the play. Shaw shows how a trivial garment can carry the whole weight of a farcical plot.