Thanks John - I'll take a photo of the whole tree and include it tomorrow.

New photos of tree attached - full tree (after rain, hence the drooping leaves) and also close up of two areas of breaking/splitting/peeling bark. It's started raining here in Seattle and I'm worried about this tree will fare. Thanks for any advice, or rx! Martha

I don't know, but John is an expert. It looks like some type of animal damage...but John will know.

It looks like phytopthria damage. - Silica

Phytophera is not common in containers; unless you are watering it with surface water (creek, river, etc.) Some rootstocks, for example carrizo, are more susceptible than others. In any case, I would paint the trunk with white latex paint.

Thanks John, I will paint the trunk. A couple years ago this tree was having problems and Patty (is she still around?) suggested that it might be the root stock had outlived it's optimum lifespan. This was my first citrus and was bought from a Long's drugstore in the CA bay area, so I have no idea what the root stock is. Patty suggested it might be a root stock that was only viable for 10 years. I'll paint it and see how it does now that we're fully into the rainy season in the PNW.