6.7 times 10 to the -3 power
0.208 seconds.
To convert seconds to milliseconds, you multiply by 1,000 since there are 1,000 milliseconds in a second. Therefore, to find out how many milliseconds are in 6.7 seconds, you calculate 6.7 seconds × 1,000 ms/second, which equals 6,700 milliseconds.
MS-67 is the "grade" of a coin. MS=Mint State and Mint state is the highest Grade given to any coin that has been in circulation. The 67 is the actual grade of the coin and the scale goes from MS-60 to MS-70. MS 70 is the absolute best grade for any coin in circulation so your MS-67 is pretty close to perfect circulated condition. There are other grades, but they are lower than MS.
67 x 365 x 24 x 60 x 60 = 2112912000
1000 millisecods = 1 second so 50,000,000 ms = 50,000,000/1,000 seconds = 50,000 seconds.