The U-943 with the large inner skirt containing the threads is on the left. and the one piece U-620 on the right. A dead give away in this case is the U-620 was fired upright with the unglazed firing rest on the bottom. Glazewelds would have to be fired upside down for best results. Thus the unglazed firing rest of the U-943 is on the top. See previous picture. Thanks for looking. More to come....