Question for Zambia Institute of Architects

I was registered as a Technician Member of the Zambia Institute of Architects in 1976 when I graduated
at the Zambia Institute of Technology (ZIT) The same year I moved to Botswana and have been working here ever since. I recently registered with the Botswana Architects Registration Council as a Technologist. I assume they accepted my membership on the basis that I was registered with ZIA before. They have requested that I ask for a letter of Good Standing from yourselves. Of course I see this as not possible as I have not been a member for over 40 years.Is there any advise you can give in this instance?