Letters to Kusum and Kapil
Osho wrote many letters to Ma Kusum Bharti and her husband Kapil, then of Ludhiana. All but a few were published in Prem Ke Swar (प्रेम के स्वर). The wiki has images of 26 of the 27 published in PKS, plus three more, 29 in all. As well, we have a few envelope images.