There are occasions when the text or arrangement of the wording in a postmark defies classification. Among these are postmarks which have both "U.S. NAVY" and the FPO address (a combination of -1 and -2 variants). Other postmarks have wording arranged such that the "t" and "u" codes cannot accurately describe them. A few postmarks have been issued with the ship's ZIP code and even hull designation/number, but not the ship's name. The code L after a major type number indicates an unclassifiable arrangement.
The following cancel is classified as Type 2(L) [S-93]
As you can see, this cancel is a mixture of several variants.
It could be a "-1" variant since it has "U.S. Navy" in the dial in addition
to the ship's name. It could also be a "-2" variant since it has "FPO" and
a ZIP Code in the dial in addition to the ship's name. Since a "-1" variant
and a "-2" variant is atypical, this cancel is given the "L" variant
instead.
Also of interest, notice that the first "A" in Shenandoah is inverted.
Locy System for Classifying Naval Postmarks, As Revised ©, of the Universal Ship Cancellation Society is excerpted and reprinted with permission.