This presents so full a series of issues that it would make a wonderful law school exam question, were law schools that practical.
First, I would try to get a sense of what the business of the company is really like. That possibly can be obtained from its website, or promotional material, or indusrtry directories, or Dun & Bradstreet or other credit reports, etc.
If the CEO promised to send you material about the company and has not, why not follow up with him -- and confirm your request, and his promise -- in a letter?
Second, I would want to get a sense of exactly what it is that the certificate for 50 shares represents. Was it 50 shares of 500 originally outstanding shares (a 10% interest in the business) or 50 of 50,000,000?
Also, if it was for 50 original shares, has the company undergone any stock splits or share dividends? If so, what originally was 50 shares could now be 500, 5,000, 50,000 or 500,000 shares.
And apart from the percentage of the original shares, have there been more shares issued later on that dilutes the interets in the business? One place to check would be to look at any possible amendments to the original certificate of incorporation and that would be in the Office of the Secretary of State of the state of incorporation of the firm.
As far as getting the CEO or firm to buy back your shares, that's a whole bunch of new issues.
Companies have no obligation, apart from contractual ones they may have agreed to, to buy back any shareholder's shares. But if they buy back some shareholders shares they may incur a duty to many shareholders. If the company is not publicly traded, your shares are "illiquid" and there is not much you can do, except find someone in the company who wants to buy them, or become become a burr under the saddle, or a pain in the a--, so the management concludes it is worth getting rid of you and thus offers to buy them back.
Then the question is price.