This company was world largest stamp wholesaler until 1970. You can read more about them at wikipedia link which is http://en.wikipedia.org/wiki/Henry_Stolow
Following are some of the Overprint stamps of Gandhi.
After reading about J & H Stolow Inc and doing more research I found out that
1) They were preparing stamp for Africa and other smaller countries.
2) They did overprinting of stamps
3) And lot more.................
One of their overprinting link is following http://www.stampnotes.com/Today_in_Postal_History/033156.html
Now after reading this link and also about the J & H Stolow I am curious about Gandhi overprint stamps from Cameroun & Nigragua which are currently selling from some european countries where this J & H Stolow has some roots.
Also I am not sure what is the real value?
If someone has any more info than please add in comments or let me know so I can update this and provide more information to current as well as future new Gandhi collectors.