Weight Tolerance For 1972 Philippine One Peso Coin.

First, some questions. Are the coins in question circulated or uncirculated? If circulated, are the lightest coins also the ones with the heaviest amount of wear? Can you measure their thickness? Does it vary from coin to coin?

I would not expect the variances you report to be found on uncirculated coins or with coins exhibiting only minor circulation wear.

I thought I'd be able to give you a definitive "official weight" answer for newly minted coins as a basis for you, but checking a few reputable sources produced a weight range of 14.00 grams (a 1972 report in the American Numismatic Association's The Numismatist magazine) to 15.00 grams (NGC/Krause) with reports of 14.28, 14.30, 14.45 and 14.50 grams in between. This variation surprised me as all of the coins were struck at the US Mint facility in Denver and wide variances wouldn't be expected.

Among your coins, I would question any with a weight of 13.21 grams (or thereabouts) as that seems especially low and outside of standard tolerance limits. Coins in the 14 to 15 gram range, especially if circulated coins, are most likely OK.

Maybe you can post a few images (especially of the 13.21 gram coin)?

Based on the images you've provided, I would say that your coins are genuine, just worn. The low-weight coins show a good deal of circulation wear (i.e., metal loss); the scale readings you are getting are not surprising.

Yes, I also found various weights listed for the coin (see above), but, just to be clear, mint tolerances are fairly meaningless once coins get as much circulation wear as your coins have (especialy the first two). The weights of heavily circulated coins will fall outside of official tolerance limits in most cases.

By way of example, the modern US five cent piece (nickel composition) has a specification weight of 5.0 grams. It has a tolerance of 0.194 grams or +/- 3.88%. If you assume a weight of 14.5 grams and a similar tolerance for the Piso, you get a tolerance range of +/- 0.5626 grams. So, any uncirculated coin in the range of 13.9374 to 15.0626 grams would be within tolerance. But, once a nickel experiences heavy circulation wear and metal loss, these tolerance limits are no longer very useful as a perfectly genuine coin could easily fall below the lower limit due to the impact of circulation.