The 1905 advert shows the address of 9 Queen's Road Central. It also matches klaus' estimated closing time of the hotel there (link).
The bank opened there 29 Aug. 1905 (Tue). Only that we may not know if it used a portion of the building, or wholly occupied. [1]
It was previously at 20 Des Voeux Road Central, earliest ads of it found back in 1903.
The right side of above shows the entry in Directory and Chronicle, with the bank's Chinese name. Seems it was used in Hong Kong and Canton area.
In fact, this name is a closer translation for 'International Banking' than the other one in Shanghai. First appeared with the 1904 edition. [2]
In north China, the bank used a different name 花旗 at about the same time, seems it is American flag related.
The International Banking Corporation of New York had been appointed fiscal agents of the U S. in Panama. [3] In other words, related to the Panama Canal project then.
National City Bank acquired a majority interest in IBC in 1915 and fully acquired it in 1919.
sources
1. Hongkong Daily Press, 1905-8-29
2. Directory and Chronicle 1904;
3. China Mail, 1905-1-23 p.4