Stephen Davies writes:
I have now learned that the second permanent Missions to Seamen premises on HK-side was at 72 & 73 Praya East.
I also know that both buildings were owned by the Hong Kong Land Investment Co. I know that the initial lease was for 3 years and that it began in 1905. It must have been renewed because the Institute stayed there until 1910 when it moved to its new premises.
He says that they started out at the Sailors Home in Sai Ying Pun, moved here in 1905, then on to the premises on the corner of Gresson Street in 1910.
An 1897 map (UKNA ref MPHH 1/412) shows 72 Praya East on the eastern corner of the Heard Street / Praya East junction, and 73 is the next building to the east. Assuming there's only a small chance the road was re-numbered between then and 1905, that's the location I've used for the marker above.