CH 1976 ATM Type 1, A1-A4, ill. letter cancelled Bern

Switzerland 1976 ATM (Frama stamps)
Type 1 with machine designation A1-A4, First Swiss ATM issue,
on illustrated letter, cancelled cancelled in the running time with all 4 values "3030 BERN GD PTT Wertzeichenverkaufstelle 06.04.78", luxury quality,
SBK 1 I-IV, ZST 1 I-IV, Michel 1.1-1.4, Seitz 1 A1-A4, Schalch 1 A1-A4.

Explanations: Duration: 09.08.1976-26.06.1978, cliché: HELVETIA (big) with license plate 'A1, A2, A3 or A4', type of digits: narrow, printing color: lilac, paper: with fibres, glossy gum, fluorescent: no surface (phosphorescent), impression cylinder: imprecisely moletted, white-greenish-blue security underprint (rosettes), color ribbon: silk ribbon I or II, printing: Wertzeichendruckerei PTT, Bern.