For these, H&K dropped the month from the date code and replaced it with the number "19" in order to completely spell out the year of manufacture.
fɔːɹ ðˈiːz, ˈeɪtʃ ænd kˈeɪ dɹˈɑːpt ðə mˈʌnθ fɹʌmðə dˈeɪt kˈoʊd ænd ɹᵻplˈeɪst ɪt wɪððə nˈʌmbɚ "nˈaɪntiːn" ɪn ˈɔːɹdɚ tə kəmplˈiːtli spˈɛl ˈaʊt ðə jˈɪɹ ʌv mˌænjuːfˈæktʃɚ.