The "Bent-Bar" (i.e., Aspen/Volare, Diplomat/LeBaron, New Yorker Fifth Avenue with factory wire wheel covers) Cars had 15x7 wheels on them. Especially the middle 1980s New Yorkers with wire wheel covers. Probably same wheel as the "cop car" wheels of the later 1970s on these cars.
That stamping is probably some production code, not the rim width.