Great Britain #724, 742 1d Yellow Olive & 1/- Bluish Violet Queen Elizabeth II, 1967-1971 Machin Head Issue, A Combination Usage on a Fine 3/4d Registered Envelope to East Pakistan, Now Bangladesh
A fine registered airmail cover to Chittagong, East Pakistan, now Bangladesh, sent from Hounslow on Augst 5, 1954. Franked with single 3d and 1/- PD perfins (Parke Davis) Wildings, paying the single ounce airmail rate to Burma. Sent by pharmaceutical company Parke-Davis to another company there. Instinct Rangoon receiving backstamps. A very scarce and unusual destination.
Our estimate of the value of this cover based on the above factors is $15. To understand how we have assessed the cover and arrived at this estimate and to gain a broader understanding of postal history collecting, I would suggest you read the article linked here. It should clarify the factors that make covers, and this one in particular scarce, and will help you to understand why we have estimated it at this amount.