Hi Kiran,
Your correct and i misspoke when i mentioned these FM's pulled configured currency. The to and from currency on both FM's are mandatory parameters. TCURR is used to get the actual conversion ratio for the currencies for a given date.
So i did more research and examining of the code and from what i can tell and from what i have seen others mention about this. The primary difference is the arithmetic itself going to and from currencies. When i say this i mean that one FM is using multiplication while the other using division as well as you can see in your code snipet some variables used in the arithmetic are different too.
What i would recommend is write a test program and do a couple of tests.
1) use the foreign FM to convert to a new currency and the local FM to convert back and validate results
2) use the foreign FM to convert to and from a new currency and validate results
3) use the local FM to convert to and from a new currency and validate results.
I think what you will find is that in test cases 2 and 3 the results may be slightly different due to level of precision in the arithmetic.
Hope this helps,
Geoffery