I love the three piece back on the D35. Always a fave of the Martin lineup.
According to "Martin Guitars, a Technical Reference" (only a lite side geek like me would own a copy) Martin stopped the practice of gluing directly to the sound board and finishing over it in '84.
FWIW, the 2009 Vintage Guitar Price Guide has a value of $1,400 to $2,000 for the '85 you are interested in. If it's "mint" then $1,800 is a fair price.
Keep us posted.
"The music business is a cruel and shallow money trench, a long plastic
hallway where thieves and pimps run free, and good men die like dogs.
There's also a negative side."
--Hunter S. Thompson
Guitars: Dean Sweet Wood 00R, Martin D2R, Guild D60, Guild D35NT, Morgan Monroe M30, OS baritone Uke