Late 80s historical romance novel, arranged marriage so the couple can do espionage, groom gives bride a paperweight, his family's traditional marriage gift.

This was a paperback, but probably over 2 inches thick. The cover may have had a cutout feature.

I believe it was set around the turn of the century. I think women wore bustles. The guy may have been European.

The couple married in Brownsville and then needed to cross the border to Mexico where (I *think* the bride had friends who also needed to be fooled by the fake marriage. The giving of the paperweight was *very* emotional bc the bride was aware of his family's tradition and knew it meant he was showing her respect in spite of the basically forced marriage in order to accomplish whatever the government's goal is.

My Google-fu is evidently not up to the task. Thanks for any suggestions!