How Young Can One Be

I have featured this photo on the site previously.  It is a trimmed (darn it!) photo, some lucky fan of Bob's obviously made it fit a photo frame.  The bottom of the photo contained the studio identification information, Robert Montgomery and MGM spelled out on the left, and RM - 1 on the far right.  Bob came to Hollywood in January, 1929, which would date the photo as being early 1929.  It may not be the earliest portrait of Bob taken in Hollywood, not all were numbered, but at least there is some idea as to when it was taken. 

I ran across the photo below recently.  No information came with it, have not seen it before.  I am guessing it was not taken at the studio.  The pose is unusual, no photography studio identification either.  Perhaps Bob set up the photo by himself?  He was a photography nut from his early youth.  The hairline is very close to what it is in the prior photo, could be an indication it was taken at or near the same time. 

I am guessing late 1928 while still in New York.  That would make him 24 years old.  But just guessing.  What do you think?  Am I in the ballpark?