Letter written on 13 May 1970
Osho wrote many letters to Ma Kusum Bharti and her husband Kapil, then of Ludhiana. Most were addressed to Kusum, but always mentioning Kapil too. 27 were published in Prem Ke Swar (प्रेम के स्वर). Sannyas Wiki has images of all but one of those published in PKS, plus three unpublished ones.
This letter is dated 13th May 1970 and was published in Prem Ke Swar (प्रेम के स्वर) as letter #17. The letterhead is a typical one of those days, showing a simple all-lower-case "acharya rajneesh" at "kamala nehru nagar" in "jabalapur (m. p.)", with his 4-digit phone number and a two-colour Jeevan Jagriti Kendra logo.
See also Letters to Kusum and Kapil