For as long as he’s been operating his eponymous menswear business—about 12 years, give or take—Sid Mashburn has sold all of his contemporary takes on classic American menswear from his own stores, ...

For over five decades, Mr. Sid has been a haven for the well-heeled men of Boston, catering to customers who might drop several grand for a well-made suit. But now, the store is hoping to attract a ...