After looking through some links to these products it appears some previous
models with the square end are no longer available, now there are L ends.
The main difference now is whether or not the MagSafe2 adapter will work;
and there is an Apple $10 adapter from Magsafe 1 to Magsafe 2 to work
where the older type adapter needs to fit newer computer. Mine is opposite
so it didn't need the adapter, and they changed the plug to an L from a T.
The original for the 13-inch non-Retina was a 60w model, so any later different
model now, may not be an official Apple product. I cannot verify, but there are
some which are clones and others that aren't. Either magsafe end may be on
a clone; and not necessarily be the correct power supply.
Usually you could use a larger output adapter than the one it shipped with if
the other specs are correct, as the load of the computer would signal the
adapter to supply more power; so an 85W may never reach that level output
when used with a computer that had originally shipped with 60W magsafe.
I suggest you take the computer to an Authorized Apple service provider and
ask they check to see if they have a listing for suitable MagSafe 85W with T end
(even if it should require the magsafe1 to magsafe2 metal $10 adapter part) or
look at the original documentation that accompanied the computer to see what
the part number was; that may be available by special order from Apple.
At this hour (very early AM in my time zone) I cannot say the part is genuine.
Good luck in this matter, and good night...!😎