Abstract: A machine printer for marking a machine readable code on envelopes and the like allows house holders and small businesses to print the postal precode on envelopes so they can be read by a machine reader rather than a keypunch operator. The printer has an adjustable jig to hold one end of an envelope, the jig has two portions which join together in sliding relationship for different sized envelopes. Each portion has a corner slot to position an envelope, and at least one of the portions has a stencil or other marking means for producing a mark on an envelope, the stencil or other marking means located a fixed distance from one corner of the envelope.