If a piece of glassware that you are trying to identify has a pontil mark at the bottom, it probably wasn't manufactured by Fenton. This is because Fenton used a different technology for manufacturing glass items. The only exceptions may be some rare pieces from 1920s.
Cruets might have cut shut marks that are similar to pontil marks. A piece with this mark could have been manufactured by Fenton or another company. Fenton items that were manufactured after 1970s usually have molded marks on them, which can help to identify the piece. However, these marks may not be visible on satin or opalescent glass. If you can't find a mark with "Fenton" written on it, try to at least locate the oval in which the word should be written. Before the 1970s, the company marked its products with stickers which often peeled off with time, so old Fenton glassware may not contain any identifying marks.
Use the 2004 guide published by Fenton to identify glassware if you are not sure about its manufacturer, pattern and age. The guides by Margaret and Kenn Whitmyer also help identify Fenton glass. Since these books are no longer in print, look for them on Amazon.com or in used book stores.