A definitive decimal currency One Rupee stainless Steel coin with a alternate milled + plain edge, first announced 2016 March 13th and first issued on March 15th(?). It was to circulate along side the older coin which remained legal tender.
Obverse : The Armorial Ensign of Sri Lanka
Reverse : The value ONE RUPEE in Sinhala, Tamil and English below and year of issue at the bottom within a circle of the traditional Sinhala Liyavela art with Sri Lanka in Sinhala on top.
Weighing each of the 100 coins on a digital pocket scale with a precision of 0.01 grams, I found that the coins weighed between 3.84 amd 3.94 with a mean of 3.90 grams. The distribution had a rms dispersion of 0.016 (0.40% of mean weight). It had a slight negative skewness of 0.084 and was leptokuratic with an positive excess kurtosis of 1.84. i.e. distribution more peaked than normal.
The CBSL press release stated All other specifications including dimensions and designs of the above said coins remain same. However the coins are 0.25 grams or 6.8% heavier.
The thickness of the Rs 1 coin varies as expected from 1.62 mm for 3.84 gram to 1.69 mm for 3.94 gram coin which are the extremes with 1.67 mm for average 3.90 gram coins.
The coin pack was obtained from CBSL on 2017 March 20th. The coin was scaned at 600 dpi and the images are displayed at 300 dpi.