DesertGold/Moorcroft: https://www.desertgold.us/moorcroft/Moorcroft.html
Moorcroft Pottery CLEMATIS Designed by Walter Moorcroft Cobalt Blue Square Ashtray Approximate Dimensions: 5" (12.7 cm) tall 1.5" (3.81 cm) rim diameter 2.25" (5.715 cm) base diameter Circa: 1946-1975 Stoke-On-Trent, England
Marked "Moorcroft England"