In this case, the letter is postmarked before the Belasco Theater opened. Just a little research turns up the fact that there was a previous theater named the Belasco, which has its own interesting history.

The theater that this letter was sent from was originally designed for Oscar Hammerstein, Sr., and opened in 1900 in Times Square as the Republic Theater. David Belasco leased the theater in 1902, naming it after himself, and producing plays starring Mary Pickford, among others.  In 1910, he relocated operations to the Stuyvesant Theater, again renaming the venue after himself. This is the current Belasco Theater.

The original theater went back to being called the Republic Theater after Belasco left, eventually becoming a Minsky’s Burlesque Theater in 1931, then in 1942 was remodeled into a cinema named the Victory. After decades of neglect, the theater was chosen as the first revitalization project in the efforts to reclaim Times Square, restored to its former glory, and reopened as the New Victory  Theater.

The New Victory is a community-oriented theater, hosting childrens’ shows as well as recitals and concerts.

http://www.newvictory.org/