I just Know My Buddy Matt, could have something on this too. So will direct this more to him but others very welcome to reply.
This is an L-52 IHS as listed in the T&T cat. However when trying to cross reference it in the Dated Cat, only listing for L-52's have a different IHS showing, labeled as MW-1. PLUS Dated cat only shows MW-1 used for 3 months, on a 26 12c, and prexy 1.5c and 3c. At first I thought I had made an error in ID'ing the type, I don't think I have. What is also kind of kewl is I have this L-52 in a horizontal format on 26, 17c, 20c, 25c and 30c. lots of other 26 denoms, coils and prexy as well as SC 720's of various months and years. Also on the War-Defense issues mostly so far IHS is from 40 to 42, ( still sorting so could be other yrs)
Now the most interesting of all these L-52's is one on a 5c Prexy over a 71 Buro. Dated Mar 57. ( I have a small accumulation of IHS's on Bureau's from Oakland but this is my 1st Chi.)
There it is ya'll so chime in with your thoughts, all are appreciated.