Don't waste your time & money with trying to inspect the quality of the weld, unless you have a knowledgeable friend. However even if you discover it's a poor weld, there's no percentage in dealing with it. It'll either break or it won't, and preventing breakage is as expensive as fixing it after.
Rear dropout doesn't lead to accidents. If it's going to break it's most likely to happen when the chain is pulling the wheel forward, and stressing it to the max. That's a compression load, so there'll be a slight shift in wheel position, but you may not even notice. After the bike will feel a bit squirrely but that's all.
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FB
Chain-L site
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