The sixth issue of Lowrys Guidon came out in near the end of 1973, but carries no date… or issue number. In fact, even the title is on the inside front cover.
Contents:
Editorial
Chainmail Additions * W.A. Rogers
Tokenism, the Robber * James Broussard
And two pages featuring thoroughly out-of-date listings for Airfix, Eidai, Fujimi, and Hasegawa models. A two-page listing of items on sale as they were dropped from the catalog, and advertisements for Short Rules and Tricolor from Guidon Games (which was cancelled, and published by TSR later).

The fourth issue of Lowrys Guidon came out in October 1972, just before the business moved to Maine. This was the final supplement to the 1972 Discount Catalog, with the 1973 Catalog coming out a few months later.
The third issue of Lowrys Guidon came out around late July 1972, after a trip to Maine to secure a larger house for the family and business. It went back down to twelve pages in the same format as the first two issues.
The second issue of Lowrys Guidon came out in April 1972, alongside the 1972 Discount Catalog and shortly after Don Lowry had acquired Panzerfaust from Don Greenwood. It expanded to 20 pages, and had a few more articles than the first issue, but otherwise kept the same format.
At the start of 1972, Lowrys Hobbies was a successful mail-order store for wargamers. However, the catalog was going out of date faster than it could easily be revised, so a supplement with updates and corrections was provided.