Which Indian motor company was the manufacturer of this Ambassador Mark 4 car?

Hindustan Motors is an Indian automotive manufacturer based in Kolkata, West Bengal, India. It is a part of the Birla Technical Services conglomerate. Hindustan Motors Limited was established during the pre-Independence era at Port Okha in Gujarat. The company was the largest car manufacturer in India before the rise of Maruti Udyog, now Maruti Suzuki. Hindustan Motors manufactured the Ambassador (Mark 1 to 4) and Landmaster motorcars (based on 1956 Morris Oxford series III), both immensely popular Indian automobiles, from 1957–2014.

The Mark 4 (shown in the picture) was the last of the Mark cars. For a short period, the cars were available as Deluxe, and later it was renamed, Ambassador Nova. The first and only integrated automobile plant in India, the Uttarpara factory, popularly known as Hind Motor, also manufactures automotive and forged components. The company also has operations in Pithampur near Indore in Madhya Pradesh where it produces 1800 cc CNG and other variants of Winner semi deck mini trucks.