The first "OH NO!!!" Moment!

...Came when I used compressed air to blow crud out of the crevice between the bottom seat boards and the seat back and sides.

Click on images to enlarge.

I discovered that in some places, it was only PAINT maintaining the surface of the board!!!!  Worms and dry rot had really excavated the lower right hand corner of the back board.

At this point I saw that I was going to really have to "go deep".  Fortunately, the eight screws holding the sides and back to the seat bottom unscrewed fairly easily.  The bottom boards are 100% sound...I do think they've been replaced.

  I had hoped I wasn't going to have to go this far, but it was clear that the seat needed to be fully dismantled to get at the damage.

I already knew that the corner nails had split out the wood, and that no filler will stick to the rusty heads, so I took the painful step of wreaking further damage on the wood by pulling the nails.  
Just as well, the lower nail was pretty much set in sawdust...

Right corner, seat back.  Yes, I can fix this.

I never knew!!

The damage is pretty localized, but there are a few worm holes along the length of the back board.  They ARE the enemy!

Epoxy repairs will be done in small areas at a time.

You'd think, why not just cut a new board?

The answer is because I cannot reproduce the subtle curve on the exterior surface of the board.  And I'm not so hot with angle cuts either.  Especially on surfaces that are cut in a faint arc.

Abatron actually will restore this board to structural integrity.

And so my work is cut out for me!  A little more than I had planned!

But that is what restoration is all about, Almost certainly, when you tackle a new area of the project, you can exclaim, "Here there be monsters!"