For me, the most classic & iconic pipes, the ones that just scream Peterson, are the 107 straight billiard and the 313 bent billiard.
The 107 is a great example of an Irish straight pipe. Big & robust yet true to form & traditional dimensions.
The 313 is a wonderful example of Peterson's patented system pipes, and is what comes to mind when I think of an Irish pipe. The 313 traces it's lineage back to the 1896 Peterson catalog. (When not carved as a system pipe, the 313 is designated as the 338).
Both are readily available today. Traditional smooth brown finish, with a nickel band and vulcanite stem are perfect! Just my .02