The Asociacion de Dependientes del Comercio is one of the oldest and most important social clubs in Havana. From my limited understanding of Spanish, it seems that the Asociacion de Dependientes del Comercio was the birthplace of the Cuba Fencing Federation.
Most of us have heard of the Buena Vista Social Club, but members-only social clubs have been a long-standing tradition in Cuba. They were cultural and social centers, where members could go to hear music and dance...and maybe gamble too. Social clubs were often segregated by social class and race or ethnicity.
Gerardo sent his regards to Miss Debbie Maris of Wilmington, Delaware.
Here's another view of Cuba. The writer of the card seems to have been called away on urgent business before even finishing the address. This was back in the days when U.S. citizens could visit Cuba without any restrictions. It's not impossible now, but it's a little more difficult.