UPDATE 1-A. Schulman offers to buy Ferro despite rejection

* Proposes $6.50/shr, a 25 pct premium

* Offer price could be adjusted after due diligence

* Ferro shares jump 29 percent to $6.74

* Offer valued at $855 million including debt

March 4 (Reuters) - Chemical maker A. Schulman Inc offered to buy Ferro Corp for $563 million nearly three weeks after being rebuffed by its rival, which makes products used in computers to mobile devices.

Ferro shares jumped 29 percent to $6.74 in early trading on the New York Stock Exchange, topping A. Schulman's offer of $6.50 per share, after the bidder said it could "adjust" its offer if it gets the chance to inspect Ferro's books.

A. Schulman's offer of $3.25 in cash and the rest in shares is at a premium of 25 percent to Ferro's Friday close of $5.20.

The offer is valued at about of $855 million including debt,

Akron, Ohio-based A. Schulman said.

A. Schulman expressed its intent to buy Ferro in a letter on Feb. 13, but was rebuffed by the Mayfield Heights, Ohio-based company. A. Schulman first contacted Ferro in November 2012.

Ferro, whose products are also found in cars and coffee cups, could not be reached for comment.

A. Schulman's main products are plastic compounds, color concentrates and additives that improve the appearance and performance of plastics in a number of applications.

"Ferro's business units align with A. Schulman's core competencies with the exception of pharmaceuticals, which is not strategic to us," said A. Schulman Chief Executive Joseph Gingo.

The expected acquisition would add to earnings in the first year following the transaction, Gingo said.

He estimated the acquisition of Ferro would lead to annual synergies of $35 million, on top of Ferro's projected savings of more than $50 million for 2014.

A. Schulman shares were up nearly 1 percent at $31.34 on the Nasdaq.