Transvaal 1885 Nice 4d Rate Zeerust to Natal

1885 Envelope from Zeerust (APR 26) to Hermannsburg, Natal franked at the 4d rate (effective since March 1877 when the ZAR and Natal agreed that the inter-colonial letter rate be reduced from 6d to 4d per half ounce). Celliers 1d & 3d cancelled with triple ring 8 numeral. Relevant transit marks, part backflap missing. F-VF, attractive, scarce franking.