Ok ... Your client has a nice chair ... this one was particularly nice as is a lot of this client's stuff. A while back, we repaired the NICEST, original finish, writing arm Windor I have ever seen. There's one like it in 's book, but it's not as nice. Here's a link to that repair story .. it's a good one and we used the same technique to repair this chair which came to us with it's arm snapped off at the joints.. Our goal is always to create new joints joints with integrity, yet leaves as much as the original wood as possible. Here's one of our best repair tricks .... click the pictures to enlarge them ...
We've excavated the broken tenons by starting with a small hole in the broken part and 'drilling up' with larger bits until we can break away the thin wall of the tenon that's left in the original hole. Then, in this case we sanded the broken arm to a point, leaving the wood on the top sanded just to the point where it broke, as it entered the mortise hole. That left us our original length to go by. Then we turned a short piece of new wood with the proper size tenon on it, stuck it int the hole and swung the arm, with it's new tenon in the front, around and traced the scarf angle onto the new piece sticking out of the back leg mortise, cut it and sanded it to fit. Carefully holding the two pieces aligned, I drilled a 3/16ths" hole for a dowel which kept the scarf joint aligned during gluing and clamping.
Get some pressure on it any way you can. masking tape is good, duct tape is stronger and stretchier, but can pull off an old finish so be careful with it.
This technique can work with almost any broken round tenon on a stetcher or spindle.
The finished chair