Another way of checking would be weight . This will tell you if it is actually thick or not or caused by an outside source without and speculation a 1961 would be a copper penny not a zinc so it would weigh 3.1 grams . the best scales are the ones that weigh better than a tenth of a gram but if it isn't a dedicated hobby you can get by with a cheapp scale as long as it is accurate. IF you check it and it is above 3.1 grams get another penny from before 1982 and weigh it as well it should also weigh 3.1 grams this will tell you if your scale is off.