Mothercare Vintage Maternity Dress

Vintage Mothercare Maternity Dress Tweed like Black with multicolore threads in a plaid like pattern The size just says just Petite in the tag Flat lay approx measurements: pit to pit (bottom of arm pit) 17" Waist : (Measured right below the buttons)17" Length: 34" (measured from v of neckline to bottom) Pull over Tie in back I put 8 for maternity size I believe this is 1980s based on the tag please let me know if I am incorrect.