I did an Internet search, and came up with this discussion from the listing on Smokingpipes.com:
"Peterson's Molly Malone set presents a fine pair of pipes named in honor of the enigmatic figure whose beauty and tragedy is the subject of the popular 19th century Irish ballad, and who is considered a symbol of the countless impoverished women of Dublin who made their meager livings as street-hawkers by day and, all too often, as part-time ladies-of-the-evening by night. For this two-pipe set, Peterson's chosen a sturdy, and rather full-bodied bent Brandy, as well as a bold and upright straight Rhodesian, each banded in sterling silver. They've also, for the box art, chosen an image of the bronze statue of Molly Malone by Jeanne Rynhart (known locally as the "Dolly With the Trolley"), which now stands at the end of Dublin's Grafton Street, and of whom it must be said, does certainly possess a decolletage positively made for marketing.
- Eric N. Squires"
I find the the idea that Peterson would create a pipe in honor of someone of low degree fascinating.