Reason for this assumption that it does not match with official cancellation issued by Post and Telegraph department of India when they issued 1948 stamps and first day cover.
This is for sale by eBay seller "straits_collection"
Now see the price $6000.!! And that's tempting to make forgeries as it's very easy to forged.!!!
It's easy to make money selling stamps on internet then working in any office or shop or factory.!!!
Read following and understand what's going on and than compare this with Pondicherry French India stamps with other cancellation available from different cities.
Forgers have not only manufactured stamps for the philatelic market, they have added forged cancellations to those stamps.
Forged cancellations have also be applied to genuine stamps, in cases where the stamps are worth much more postally used. In addition, where rare cancellations are desired by collectors, those cancellations have also been forged.
Cancellations also may be used to prove that certain philatelic items are genuine. For example, forgers have fabricated many supposedly valuable postal covers by adding genuine stamps and forged postal markings to pre-stamp covers. (From Wikipedia)
Majority are FORGERIES or Bogus.!!
1) G.P.O missing on Simla, Nagpur and Shillong. WHY ? ( Genuine or BOGUS or Forgery)
2) Alphabet type and size : Shillong, Delhi, New Delhi
3) Shapes of special cancellation (Madras)
4) Is it AUG or AUGUST.
5) Compare lines and size inside the cancellation
6) Compare Hindi languague alphabet "जय हिन्द"
7) All kinds of different things you can think and compare.!!
But there are more forgeries of this cancellation than any cancellation in stamp collection history.!!
In this forgery cancellation, it has been have push to collect cancellation from different post office in India.!!
So forger created for you cancellation from Simla, Patna, Allahabad, Poona, Nagpur, Kanpur, Pondicherry, and lot more hiding in someone collection.!!
Want to make money than just make this Jai Hind special cancellation from some other cities and sell it as RARE.!!
Gandhi Stamps Club.
I wish some one buys this for $6000 so eBay get commission and shareholders get rich.!! ( Disclosure : I am holding eBay stock to become rich.!!)