The blocks we have here have different suffix numbers the 1's are always smooth with very little flashing on them. The higher numbers usually have large flashings and bad porosity. The end of the ladle always is the worst metal of the pour. I worked at a foundry in the Bethlehem steel in the 70's The best parts always came from the start of the ladle after scraping the slag from the top . The last of the pour was always dirty and cooler. It is usually the dirty iron not having the same flow Characteristics as it cools. The Higher numbers are the end of the pour.