I just picked up a NIB 6" 29-3 for $600. It was $550 in last year's blue book. I think the market value on most firearms has increased a little since then.
The last 36 flat latch blued 90% I priced was 295.00. I have seen them up to 325. The Mod 29, proably, should fall in the 495. to 550. 90% generally gives you some dickering room. Good luck. Keep in mind, this is in my neck of the woods. I have heard of other parts of the country bringing higher prices, as well as lower.
Heck.....You can't get a 90% flat latch model 36 for any less than $ 500 in Arizona.
Of course they are not selling, but they keep bringing them back to SHOW, AFTER, SHOW.
MIne is 1957 and is $525 if I decided to sell it."NOT"