I have had one cracked there myself when restoring Model 10E S/N 17731. I replaced it with the later Tie Bar.
It wasn't too long before the extra material was added as shown in the second picture below. The highest serial number I have had for a 10E with the early Tie Bar is 19541. A picture of the early Tie Bar (like yours) is shown in the first picture below. Model 10E S/N 25951 is the lowest one I have had with the newer casting of the Tie Bar shown in the second picture below. The casting changed but the part number did not. The Tie Bar version's part number 101-3 and later C 2267 (although the part itself still said 101-3) are interchangeable. This is a case where a single part can be replaced with a later (or earlier) part individually. Some parts have to be changed as an assembly. I should add, for clarity, that all Model 10ER part numbers changed in November of 1951.
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Yes, some of the markings changed on the castings during production.
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