I have a 70's Mugen 12-string which my brother bought for £2 at a car boot sale It had two cogs missing from the open machine-heads, no strings attached, and a two-inch split which has been completely stable. The bridge lifted once, but was easily repaired, and I now keep it tuned a tone down to lessen the strain. It is of course a Martin clone, plays just like one, and sounds amazing.