Wow! That was fast. I figured it was an L-Type since I don't have a catalog with those listings to compare it to. Thanks for the info.
Needless to say, I've been going through an accumulation of Michigan precancels. Just for fun, take a look at these Detroit precancels:

First, they are cancelled over the precancel, which although not unheard of, sort of defeats the purpose of precanceling a stamp.
Second, it looks like someone was playing with a pair of scissors on the first three stamps.
The center two stamps are both stamped Buffalo, NY and both with what looks to be the initials "HERT" in the center. Any idea what this meant? Maybe some "terminal" or something?
The last one has a purple rubber stamp overprint that appears to be an "Unclaimed...Return to Sender...N.Y.P.O. ... Postage [Due?].
Nothing extraordinary, just interesting to see what you can find within an accumulation of precancels!