Business Source 04441 #3 Coin Envelopes, 2-1/2 x 4-1/4″, 20 lb. Brown Kraft, Box of 500. Handy little coin envelopes are ideal for small parts, samples, seeds, enclosures, loose coins and payroll applications. Flaps feature deep gumming for a secure seal. No. 3 coin envelopes are made of sturdy 20 lb. Kraft stock.