Steven,
A little info for you.
I was interested in your letter thinking the Mr Doyle could be Larry Doyle.
When I looked up Doyle and Tigers coaches I found that no person named Doyle has been a Tiger coach. It's on the Detroit Tiger website.
http://detroit.tigers.mlb.com/det/history/coaches.jsp
Perhaps this person is a scout or minor league coach/manager.
I would be interesting to see the envelope for a destination address. Larry Doyle was likely in the Sarnac Lake, NY Sanitarium at that time, being treated for TB.
Another tidbit is the person named Pat on the third page is, I think, Pat Haley. He was the manager of the 1929 Wheeling WV Stogies, where a 22yo Bridges went 10-3 with a 3.14 era.
Mark