This building held a series of studios, any one of these could be the photographer doing business under the name of The Flashlight Studio.
The photographer may be Burns, because the style of the stamp is so similar to his.
1893 E. Corbett.
1897-1900 Joseph S. McClellan
1903 Green & Maddock
“The Flash Light Studio. 508 Williams Ave. Portland, Oregon (Upper Albina)” rubber stamp on cabinet card back.”Electric Flash Light Company” ms date 1895.