Ithaca/SKB 200E rattle

[all4abuck]

I inhereted a 20ga sxs ithaca/SKB 200E shotgun from a family member.  I am not familiar with sxs guns as I have never owned one before.  The gun looks great and I like to take it out and try it.  However I noticed a rattle when I was handling it.  All the parts fit and no movement, but I can hear something like a screw or spring lose in the stock side of the action when I shake the gun .  Seems to be rolling around in there.

Any idea what could this be?  I will take it to a gunsmith but just want to get an idea of what I should expect.

Any help on this will be appreciated.

[spruce]

I have an Ithaca/SKB model 100 - essentially the same gun as yours, but with extractors.  Bought it new in 1967 (?).  Never had any issues with it, used it a LOT over the years.

This may sound too simple, but have you taken the butt plate off to see if maybe someone stored something in the stock bolt hole?

It's possible the stock bolt has worked loose and is rattling.  I think the close fit of the stock to the upper and lower tangs plus the screw in the lower tang may still hold the stock tight even if the bolt inside is loose.
Just a couple simple things to check before you pay a 'smith!

[all4abuck]

Thanks for the reply spruce.  I removed the butt plate and couldn't find anything there.  I noticed a wedge was added there to change stock angle.  But other than that, nothing seem to be loose.  The noise is coming from right around the coin finished receiver.

As far as disassembly, is there an article or schematic out there that I can get a hold of?  Just don't want to screw up something I cannot fix.