Just for the interest of Domainers:
There are two types of 'Limited' companies. 'Limited by Shares' and 'Limited by Guarantee'. Most of us know about companies 'Limited by Shares', which again are divided into two types. 'Private Limited' and 'Public Limited'. Public limited companies, also called 'PLCs', are further divided into two classes 'Listed' and 'Un-listed'. (Listed means whose shares are traded at 'Stock Exchanges').
TLD has got nothing to do with LTD. Limited companies have been there since the year 1800+somthing, whereas TLD is still an 'Infant'.