Indonesian 100-rupiah coin

The Indonesian one hundred rupiah coin (Rp100) is a denomination of the Indonesian rupiah. First introduced in 1973 in cupronickel, it has been revised four times throughout its history, changing materials in 1991 (to aluminum-bronze) and 1999 (to aluminum). As of 2022, it is the second-lowest valued coin of the rupiah after the now-rarely encountered Rp50 coin.

First series (1973)
The 100 rupiah coin was first introduced in 1973 as a cupronickel coin weighing 9.72 g. It had a diameter of 28.5 mm and was 1.77 mm thick. Its obverse featured the denomination ("100") in its center with the lettering "BANK INDONESIA," two stars, and the mint year (1973). Meanwhile, its reverse depicts a rumah gadang, a traditional house from West Sumatra, as well as the lettering "Rp 100" on top of it. Its edge was smooth and featured the lettering "BANK INDONESIA". 252,868,000 coins were minted bearing this date. These coins were demonetized on June 25, 2002, and was redeemable in general banks until June 24, 2007, and in Bank Indonesia offices up to June 24, 2012.

Second series (1978)
In 1978, this coin was updated, now as a FAO circulating commemorative coin. The rumah gadang was moved to the coin's obverse, while its reverse now features a depiction of a gunungan, an element in Javanese wayang, over a depiction of a globe. At the same time, the lettering gets updated, with its obverse now featuring the letterings "BANK INDONESIA" and "SERATUS RUPIAH" while keeping the two stars, and its reverse now featuring the lettering "HUTAN UNTUK KESEJAHTERAAN" (FORESTRY FOR PROSPERITY) and the denomination as well as the mint year (1978). This coin was also made lighter and thinner, as it now weighs 7 g (as opposed to the 1973 coin's 9.72 g) and was 1.4 mm thick (instead of the 1973 series' 1.7 mm); however, its diameter remained the same at 28.5 mm. Furthermore, the "BANK INDONESIA" lettering, once etched to its edge, was removed; with the edge itself being made reeded. 907,773,000 of these coins were minted in total. These coins were taken out of circulation on June 25, 2002, the same date as the 1973 coins, and were redeemable in commercial banks until June 24, 2007, and in Bank Indonesia offices until June 24, 2012.

Third series (1991-1998)
In 1991, this coin was updated for the second time. Now minted in aluminum-bronze, it had a diameter of 22 mm, thickness of 1.6 mm, and a weight of 4.13 g. It had a smooth edge with no lettering, as opposed to the 1978 design's reeded edge and the 1973 design's carving of "BANK INDONESIA." Its obverse featured the national emblem Garuda Pancasila, the lettering "BANK INDONESIA" (now made smaller and placed on the bottom), and the mint year (1991-1998), while its reverse featured a depiction of karapan sapi, a Madurese bull-racing event, the denomination (Rp 100), and the lettering "Karapan Sapi." These coins were demonetized on November 30, 2006, and was redeemable in commercial banks until November 29, 2011, and in Bank Indonesia offices until November 29, 2016.

Mintage figures of this coin are as follows:

Fourth series (1999-2005)
The coin was updated for the third time in 1999, with its material switched to aluminum. It had a diameter of 23 mm, thickness of 2 mm, weight of 1.79 g, and a smooth edge. While its obverse remained unchanged as the 1991 series, its reverse now featured a depiction of the palm cockatoo (Probosciger aterrimus) as well as the lettering "KAKAKTUA RAJA" (PALM COCKATOO) to its upper right and denomination (100 RUPIAH) to its lower right.

Fifth series (2016)
As part of the release of the then-new National Heroes series of rupiah coins and banknotes on December 19, 2016, the coin was updated for the fourth time. Its obverse now not only features the national emblem (now moved to the upper left), but also a depiction of Prof. Dr. Ir. Herman Johannes to its right, as well as the letterings "REPUBLIK INDONESIA" on top of both images and "Prof. Dr. Ir. HERMAN JOHANNES" to its bottom. Meanwhile, its reverse now featured a simple depiction of the denomination, the lettering "BANK INDONESIA," and the mint year (2016).