having trouble with LOOKUP function returning spurious results

attached a sample file. I have column with 3 letters in each cell excerpted from using the LEFT() function on the adjacent column to right. made a lookup array that I believe contains all possible combinations of the 3 letters to be found in the list and desired text return for the function.

But LOOKUP() returns only a few correctly. With others it picks the wrong value and others it throws an error. I checked for spaces or other problems. Obviously I haven't got something right. I tried it both with the array style formula, and the compare and return ranges listed separately with a comma separating and get the same results with both approaches.

thanks anyone who can tell me how to attach the file so i might some help seeing what i can't.

frustrated in exeter

PS, i'm not sure what the attachment icon above the posting window is about. It doesn't show that i have anything attached not allow me to make attachments. i used the manage attachments below the posting window.