Company buy back of shares, capital treatment, 5 year rule

 My client has some shares in a private trading company which he would like to dispose of. He can't find a willing buyer, but the company is willing to buy back the shares. He acquired just under 5% of the company in a number of transactions over a period of time and a year or so ago transferred some of his shares to his wife. He currently holds just over 2%, his wife just under 3%.

He originally acquired 2% of the company more than five years ago, and the situation meets the other requirements for capital treatment on a company buyback, so at least some of his shares should qualify for capital treatment.  The question is, how many? My questions are:

-- if  the company buys back 2% of his shares, can he in effect treat these as being the oldest ones he acquired so that he qualifies for capital treatment on the full amount?  

- Alternatively  is it assumed that the transfer to his wife comes pro rata from each of his own individual acquisitions, so that some of the 2% owned for more than 5 years has already been transferred to her? 

- With respect to the shares transferred to his wife, does the five-year clock start anew on these shares following the transfer, or is there some rule whereby she can treat the shares as acquired when her husband acquired them for these purposes?

I'd be most grateful for any thoughts.