I have attached a photo of four ShVAK rounds from the collection. Left is the HEI-T round (1944 headstamp) with the K-6 fuze. Next is the HEI-T (1951 headstamp) with the A-20 fuze. Next is an API round with a 1942 headstamp. The last (far right) is a Czech made (iou 52) loading. Can someone tell me if this is an AP, APT, API?