Peerless Theodosia was published in March 1980 by Fawcett under their Coventry Regency Romance line. Note the #30 in the corner. This book is about Theodosia and her brother, who are American and come to visit the Southcote family and the havoc that reigns afterwards. Glancing through this book, it reads like a tribute to Georgette Heyer's The Grand Sophy.
The illustration that Allan Kass has drawn surely would fit the cover of The Grand Sophy with a heroine who adores green, is dressed well and delivers a parrot to the children of the family. This is a beautiful cover showing the heroine in a traveling dress with her large muff, which was very popular to carry, and a plumed hat. Outfits like this would have been sewn with fabrics like velvet that could be easily brushed down and also kept the wearer warm. Note the doorway! Theodosia arrives at a London townhouse with a Georgian/Palladian entrance which doesn't look out of place nowadays. Normally the butler would have opened the door and footman would help her with her things. Regency townhouses were narrow in front, but long in depth, sometimes rising 4 to 5 stories. In the US, you can see houses similar to this in Charleston, South Carolina. In the UK, visit Bath to see a preserved Regency townhouse at #1 Royal Crescent!