The 2017/18 order which was issued on 2018 December 3rd made all the coins smaller to save on cost of minting the coins. All are cost cutting measures were marketed with weight of coins is reduced to give more portability.
The basic design layout of these standard circulation coin has been changed significantly. For the first time since the circulation standard one Rupee coin was introduced in 1963 in the Sinhala only era, the name of the country appears on it in Thamil and English.
The design has on obverse the Armorial Ensign of Sri Lanka with short name of country in SRI LANKA in English, ශ්රී ලංකා in Sinhala, and இலங்கை in Thamil, on left, top and right of ensign, with a decorate between them. Year 2017 at bottom, all within a plain circle inside a raised rim. On the reverse large numeric value on top with the value in Sinhala, Thamil and English, in three lines below with decreasing font size. All within a border of traditional lotus petals around the periphery.
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| KM | One | Rupee | Stainless Steel | coin | 2017 | Kremnica |
| KM | Two | Rupee | Stainless Steel | coin | 2017 | Kremnica |
| KM | Five | Rupee | Stainless Steel | coin | 2017 | Kremnica |
| KM | Ten | Rupee | Stainless Steel | coin | 2017 | Kremnica |
A presentation box was given to former President Mahinda Rajapakse on
November 27th by the Governor of the Central Bank Indrajit Coomaraswamy.
Although the Coin set gifted to MR has a serial #0001 CBSL informed me
that only a few presentation packs were sent by Kreminca Mint and none
will be sold to the public.
The coin has specified to mint by metal Chromium Stainless Steel ASI430, diameter and thickness. The weight was not specified and therefore was not stated in the Press release, or in the printed specifications in Sinhala, Thamil and English, put in the zip-lock bag of mixed set of 5 coins each and an extra Rs10 to make up Rs100.
I measured thickness of the coins in 2 packs and the statistics are given below.
| Face Value | Rs 1 | Rs 2 | Rs 5 | Rs 10 | |
| Diameter mm | 20.0 | 22.0 | 23.5 | 26.4 | Specified |
| Thickness mm | 1.75 | 1.75 | 1.80 | 1.80 | Specified |
| Mean Thickness mm | 1.72 | 1.73 | 1.69 | 1.65 | Measured |
| RMS Thickness mm | 0.018 | 0.025 | 0.032 | 0.053 | |
| RMS as Percent % | 1.0 | 1.5 | 1.9 | 3.2 | |
| # Coins measured | 10 | 10 | 10 | 12 | |
| Thickness 2009 mm | 1.7 | 1.5 | 2.4 | 2.1 | Measured |
The weights of coins in a pack of 100 were measured to 0.01 grams and the statistics are given below
| Face Value | Rs 1 | Rs 2 | Rs 5 | Rs 10 | |
| Mean Weight 2017 gms | 3.76 | 4.48 | 5.25 | 6.43 | Measured |
| RMS Weight gms | 0.016 | 0.022 | 0.020 | 0.032 | |
| Skew | -0.075 | 0.437 | -0.590 | 0.274 | |
| Kurtotis excess | -0.42 | -0.11 | 0.45 | -0.80 | |
| RMS as Percent % | 0.43 | 0.50 | 0.37 | 0.50 | |
| # Coins weighed | 100 | 100 | 100 | 100 | |
| 2017/2009 wt ratio | 1.03 | 0.64 | 0.68 | 0.77 | |
| Mean Weight 2009 gms | 3.65 | 7.00 | 7.70 | 8.36 | Published |
The weight has about 0.5% rms variation as expected. The mean thickness of all of the coins are less than specified by CBSL to Mint. It was estimated to be 6% and 8% less than specified for the Rs 5 and Rs10 respectively. Weight is clearly better defined than thickness, which more difficult to measure precisely, and showed a larger rms variation of 1-3%, when we could expect only 0.5% from error in weight. 0.5% of thickness is 0.01 mm or same as the measurment precision of thickness. The bigger RMS in thickness maybe random measurment errors, because of raised text on coin. Maybe thickness was to the top of high relief. More coins will need to have thickness measured to obtain better statistical estimates.
Read my expose in SundayTimes of Sri Lanka of 2018 December 2nd Busines Times page 4 bottom titled New Smaller Coins into Circulation
On 2018 December 3rd CBS: issued zip-lock bag of mixed set of 5 coins each and an extra Rs10 to make up Rs100. with printed specifications in Sinhala, Thamil and English. Initially from 9 AM they had sold with a max of 5 packs each, but when I went 15 minutes before Cash Counter closed at 12 Noon, I got the last 2 packs.
Since coins have a long lifetime, it is curious why the number of 2017
coins ordered for 2017/18 is more than five times the increase in
circulation of coins of the same denominations in the year from August
2017 for which CB data was published. The 2017 coins remained in the
CB vault for over a year before being issued. The one and two rupee
coins still cost more than face value to mint. So why mint them when
they may never be used? The same happened with the 25 cent and 50 cent
coins minted in 2009.
In 2019 February I was told that CBSL was building warehouse to stock
the excess coins minted. Subsequently in 2019 they opened a cash
counter in CBSL and issued as many bags of coins as you needed to
reduce stock as fast as possible.