Some further info on Sandwich overshot. I have a copy of a catalog used in the Boston & Sandwich Glass Co. offices c.1874. It consist of period photographs of good quality with black background. 79 pages in all. Two pages are devoted to overshot. Of the two pictures of bladder jugs shown both are the standard shape in question. One has the handle attached below the bladder the other above. Handles are fairly standard nothing fancy. Although the baskets have clear twisted handles much taller than the baskets themselves.
On May 3, 1877, the Crockery and Glass Journal printed a report sent to them by their New York correspondent. He had visited the Boston & Sandwich showroom located at 23 Barclay street in New York City. After a lengthy discussion of all the glass he had seen, he discussed frosted glassware [ the term used at the time for overshot], including flower baskets, finger bowls with underplates, champagne jugs [ pitchers with ice bladders ] and punch bowls. He wrote that all these items were fully equal to those imported from abroad, and that the champagne cooler commended itself to those who preferred wine without water.
As to pontils ground or otherwise I have no information.I assume they were left rough unless it protruded to much. One standard pitcher in the previously mentioned guide was machined on the bottom to level it.