I believe the legend of your coin is 10cf rather than ab, though there are the occasional exceptions.
Your coin is missing a lot of information at key points, but the crown, whilst double-struck, is very much in the 10cf5 camp for me, with the left arrowhead ornament leaning left, and the left fleur in its broken configuration.
See Blunt’s crown 5 examples here (one with the broken left fleur), with yours (next post) for direct comparison.