A Kuala Belait Retour cover

I am gradually building up my Retour cover collection. This is one of my particular favourites as it tells an interesting story of its journey through the mail system. You can use the search bar in the top left hand corner of this page to look for other retour items on this blog. And at the top of the right side is a google translate facility for changing the text into a language of choice. But I can not vouch for the accuracy of translation.

It was sent by the Chinese Labour Union in Kuala Belait to their counterpart in New York but unfortunately with the wrong address. It was posted on 4MR47 and dispatched on 6MR47. It has a rudimentary K Belait registration label and marked in manuscript Air Mail Registered. It was also handstamped Air To London Only in violet probably at Singapore. It bears adhesives to a total value of 70c for a combination of surface and air mail rates which included transmission by air mail to London only.
There is a Singapore transit registration postmark for 5 pm 17 MR 1947. It arrived at New York on April 5 1947. Delivery was attempted and failed despite trying a possible address. It was struck with a Retour cachet on APR 7 1947 with a linear date on the front and a cds at the back, both in violet. It was also written in pencil on the front with not at add given 0144. It stayed on at the New York P O until it was returned as seen on the oval cancellation for 7 May 1947. It arrived back to Belait via Singapore with a transit cancellation for 2 pm 15 JU 1947.
Update This Air To London Only handstamp is recorded by Proud as Sandakan AM8 with one date recorded of 25.3.47 and so that gives rise to more questions.