Arne Jacobsen Mosquito chair refinish/repair  

Why would you sand it at all? Sanding removes the wood cells on the surface that have darkened with age and that give the chair its patina.
Go over it with #0000 steel wool and teak oil. The oil will loosen any grime on the chair in addition to making the wood look great, and it also lubricates the steel wool and minimizes any marks left by it. Do long strokes with the grain and use even pressure, starting with light, over the whole surface. Wipe with clean rags or paper towels and buff again about a half hour later.

OK! Great info Spanky. I will proceed with your instructions since you are so helpful and knowledgeable and willing to share your expertise. Is the Watco Danish teak your favorite or would you have a better product in mind? Also, would you recommend just one coat?
Thanks a mil!

Spanky is not going to recommend Watco. And in fact Watco will not work nearly as well for a Spanky's technique.
What was the original finish on these chairs, though? Was it an oil finish? A lacquer finish?

Yes--first figure out the original finish! I kind of assumed it was oil but of course it might not have been. You can test for lacquer in an inconspicuous spot by dabbing acetone (nail polish remover) onto the finish with a Q-tip. Lacquer will begin to dissolve immediately.
Watco is great if you want the kind of finish it imparts and you are willing and able to put more time into finishing. I've used it and was happy with the results. Most of the time I just do Star-brite Teak Oil (Ace Hardware carries it). I do believe you could use it to at least loosen and remove grime before doing a harder oil finish like Watco. (Watco has added varnish; Star-brite has none.) Other people use mineral spirits to remove grime but I prefer oil.

Thanks Spanky and Leif!
I believe the original finish was oil based without a high sheen or over the years it has worn away. Most of the plywood images I see of these period pieces are refinished in a higher gloss that I personally am not fond of. One of the chair's edge has what appears to be numerous, small indentations along with some veneer chipping so I wanted to be careful while prepping so that I don;t lose any more veneer. What in your opinion is the best filler for this type of application?
Thanks so much for taking the time to help me with this project!

I can't advise you on wood fillers or veneer repair, but I can recommend that you rotate your chairs once they're in use so that each one gets about the same amount of wear over time. I do paper cord weaving for people and I can't tell you how many sets of chairs I've seen where two or three out of set of six are absolutely shot and the rest are still OK---but all have to be redone if the cord color is to match. If you just move each chair clockwise one place around the table, say, every time you clean the floor (or a couple times a month at least), you'll form a good habit that will benefit your chairs. If they're used elsewhere in the home, then figure out some other way to remember to rotate them.

Very good advice! I used to know a furniture store manager who recommended something similar with sofas as well as chairs with cushions. He said that it was best to rotate (flip) cushions often if possible so that they would wear evenly. He called it "cushion management"!

I'm sorry…I meant to say "regulate" the cushions in the previous comment!