can anyone tell me if a 29 no dash with serial number starting with s186xxx could have come in a wood box?

I think yes, but I am confident somebody with a more solid answer will come along soon.

I had one in that range that was in a "clamshell" presentation case. The style of this case has a molded in (styro covered with flock) profile in both the upper and lower lids. Though, I cannot verify that the gun actually shipped with the case.

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Randy
Provenance nerd

A Model 29 in the S186000 range most likely would have shipped in 1959 when the dark blue/black presentation case was still in use. The mahogany case with Styrofoam inserts ("clamshell" interior) was generally introduced in the spring of 1960. There are some mahogany cases shipped with Model 29s in 1959 that have a cloth lining like the dark blue/black cases, but these are most common for 44 Magnums with an 8 3/8-inch barrel since S&W did not make a dark blue/black case for this barrel length. I have only seen one presentation case like this for a 4-inch and one for a 6 1/2-inch Model 29.

Bill