During the Colonial period and continuing up to the introduction of adhesive stamps, letters were typically sent collect, the postage to be paid by the recipient upon arrival. The covers, or envelopes in which the letters were sent, were stamped by hand with the name of the originating town, and typically with a number representing the charge for postage, e.g., "3" for 3 reales. Occasionally, mail was sent postage pre-paid, in which case the envelope would be marked "Franca" or "Franco" or "Franqueado." According to Yag & Bash (1965), some handstamps (on undated covers) date to the 1720s and the earliest known stamped postmark on a dated cover is a Veracruz mark from 1736. Yag and Bash researched the Chapman records, and found these numbers of post offices: