Hi Kark and Joe
On the Anatomy of the ship "The Flower Class Corvette Agassiz" page 29 (top picture) it shows HMCS Snowberry... although not a clear shot of the gun shield and comparing it with the decals, aparently it misses the black lines, which could be handpainted after aplying the decals to the shield.
My guess is that this is a little mistake by Revell or originally by Matchbox, that can be corrected, with some work.
Karl, I strongly advice checking
Graham Townsend HMS Campanula MOD Feature just for fun or for reference on some of the upgrades (if you want to go the extra mile).
Hope this helps
Skipper