As far as I have been told the only thing to look out for on Pattern 1914's is cracks on the receiver where the barrel meets it. There is no known difference between makers. It could happen on any rifle. It is a result of how the barrel was attached to the receiver, they could apparently easily apply too much pressure and inadvertently crack the receiver. Rebarreled examples are obviously more at risk. Unlike the M1903, there is no specific serial block to avoid. As far as I understand the "upgrade" to Mk1* involved the length of the locking lugs on the bolts, but this was not done for a safety reason. It was done for the convention of having all three makers make them to the same specifications.

Oh, forgot to add, I have an unstared example that I shoot all the time, but as others have said, take that information as you will.