As stated by boubonv, Haig & Haig did produce a 4/5 Pint (largely in the 50s-60s), as well as a 1-Qt, 26.6oz (Imperial Qt), 4/5-Qt, 1-Pint, 1/2-Pint, 1/6-Pint & 1/10-Pint.
I have a large collection of sealed Haig & Haig brands (Gold Label, Five Star, Pinch/Dimple, etc), including nearly all of the sizes dating from a variety of periods (1930-1960).
As for researching your bottle, if you need assistance I can be of help on that...Here's a few quick pointers:
1) The Cap-style you have there is called a "Spring-Cap", which was produced from 1928-1970 and used on Haig & Haig export bottles mostly from 1930-1965.
2) The Red Federal Tax Strip across the top of the bottle, shows the proper weight for the bottle, and would date this between 1933-1977 (in '77 they removed the weight marking).
3) The Footer-label indicates a "...Under Supervision" notice, confirming it was produced after 1939 (British Law requires this disclaimer from 1939 to about 1975).
4) The Tax Strip is also marked as imported by Renfield Importers, who had exclusive distribution rights to the US starting in late-1946 (Somerset Importers had exclusive rights prior.)
5) On the Shoulder-label, your bottle is marked with a location of Markinch, indicating your bottle was produced after the company had moved it's headquarters in 1950-51.
....So far we have narrowed it down to a bottling date between 1951 (Haig's move to Markinch) and 1965 (end of Spring-cap usage by Haig & Haig).
There are some additional details that we can look at in order to try to bring a it down to a closeer bottling date if you wish...I can usually get it to within 3-5 years on most blends.
Walter C Hurst