The coins and currency reforms of Sher Shah Suri (Sher Khan) are one 
of his most outstanding achievements. Sher Shah Suri found on his 
accession that the currency system had practically broken down. There 
was debasement of the current coins and the absence of a fixed ratio 
between the coins and various metals. There was another difficulty, 
namely, that coins of all previous reigns, in fact of all ages, were 
allowed to circulate as legal tender.
Sher Shah Suri took steps to
 issue a large number of new silver coins which, subsequently, became 
known as dam. Both the silver rupee and copper dam had their halves, 
quarters, eighths and sixteenths. Next, he abolished all old and mixed 
metal currency coins. He fixed a rate between the copper and silver 
coins. His silver rupee coins weighed 180 grains, of which 175 grains 
were pure silver. This rupee minus its inscription lasted throughout the
 Mughal period and was retained by the English East India Company up to 
1835. V.A. Smith rightly observes: "it is the basis of the existing 
British currency" (up to 1947).
Sher Shah's name and title and 
place of mint were invariably inscribed on the coins in Arabic 
characters. Some of his coins bore his name in Devanagari script and 
some had the names of first four Khalifas in addition. Gold coins of 
pure metal of various weights, such as 166.4 grains, 167 grains and 
168.5 grains, were executed. The ratio of exchange between the dam and 
the rupee was 64 to 1. The ratios between the various gold coins and the
 silver ones were fixed on a permanent basis.
These coins and 
currency reforms of Sher Shah Suri proved very useful and did away with a
 great deal of inconvenience which was experienced by the general public
 and particularly by the trading community. These reforms have elicited 
high praise from modern numismatists.
"Sher
 Shah is entitled to the honour of establishing the reformed system of 
currency which lasted throughout the Mughal period, was maintained by 
the East India Company down to 1835, and is the basis of the existing 
British currency. He finally abolished the inconvenient billon coinage 
of mixed metal, and struck well-executed pieces in gold, silver, and 
copper, to a fixed standard of both weight and fineness. His silver 
rupees, which weigh 180 grains, and contain 175 grains of pure silver, 
being thus practically equal in value to the modern rupee, often have 
the king's name in Nagari characters in addition to the usual Arabic 
inscriptions." (V. A. Smith, Imperial Gazetteer of India, ii, pp. 
145-6.)
"His coins also illustrate the rapidity with which he 
conquered the countries settled under his rule. The land survey, 
construction of roads, and establishment of mint towns seem to follow 
almost in the wake of his conquering armies." ( Qanungo, Sher Shah, p. 
383.)
".........He reformed the coinage, issuing an abundance of 
silver money, excellent in both fineness and execution. That is a good 
record for a stormy reign of five years. If Sher Shah had been spared he
 would have established his dynasty, and the ' Great Mughals ' would not
 have appeared on the stage of history." (The Oxford History of India, 
pp. 327-29.)