The needle down heel tap feature was introduced about 1984, during the 930 production period. The "serial number starting with 24 or 25" is generally correct (since 24xxxxxxx indicates a machine built in 1984. However I have a Bernina 910 built in 1983 (serial number 23xxxxxxx) an I DO have the needle up/down. The machine has to have the right internals - and also the right foot control. The foot control for the needle down feature is Type 365 or 366. The foot control before the needle down was added is Type 346 or 347. Of course, you could have the wrong foot control if it was replaced or traded in the meantime. When I bought my 910, it had an generic foot control as the Bernina one had broken (and I negotiated a lower price because of it). When I finally got a Bernina foot control for it I discovered that is had the needle down feature. Lucky I had found a Type 366 foot control.