As indicated by the caption, this image shows four footmen dating to 1904. They appear to be standing outside the west portico.
The caption accompanying this photograph reads as follows:
1904: Harbor Hill footmen
The same photograph is reproduced again but with a different caption:
Four footmen. Their silken liveries are ornamented by silver buttons and their shoes, by silver buckles
See Harbor Hill, Clarence Hungerford Mackay's Mansion.