1、窄距壹圓。
2、飛雁與東北四四混貼。
3、三枚壹圓自左至右為「小臺撇幣」、「大臺撇幣」、「大臺撇幣」。

There was a seller who sold about 10 to 15 covers sent from Taiwan to Bank of China in Havana Cuba  two years ago. Most of them were flying geese covers. I only managed to acquire the first cover he sold since it was relatively inexpensive. (See link below. No. 14 posting). The rest of the covers were too expensive for me to acquire.

http://chch.idv.tw/phpwind/read-htm-tid-23310-fpage-0-page-2.html

It is possible that someone in the bank kept most of the covers till they closed the bank.