what it indicates, if certified copy of sale deed is different from original sale deed?

Sir,

I Nagarjuna from Guntur district of Andhra Pradesh proposes to buy an open land. in that process i approached the seller and obtained the xerox copies of the property which he proposed for selling.

In the process of verification of genuinity of the sale deed, i applied for certified copy with the Sub registrar office and i got it. After verifying the certified copy with the copy of sale deed taken from the seller, it is observed that signatures are completely different in both the copies. The document is belongs to the year of 1998.

What can be understand from the above mis matches?
can i buy the above property?

Sir, please kindly reply for my query. Thank you sir.