I am a (your job title) at (name of your company) where we (describe your company's process, operation or product).
Several of our company's representatives would be interested in visiting your company, in particular because of your reputation and to observe first hand your machine operations and processes. In return, your representatives would be welcome to visit our company for the same purpose.
You can contact me with your decision and if favorable, we can arrange a date which would be mutually acceptable.
Hoping for a favorable response, I am
(Name, Address, Tel.)