Both types are found on compact, untested deposit safes — an affordable solution for setting aside daily takings during the day. The difference lies in the opening.
A deposit slot, as on the Technomax Trony, is a narrow opening for banknotes and envelopes. Its small size makes the contents hard to reach, and since a slot has no moving parts, there is little that can wear or break. A slot can often also be fitted to a regular safe — keep in mind, however, that the safe's certification is then voided. Coin rolls or thicker bundles will not fit through a slot.
A deposit flap, as on the Salvus Monopoli, offers a wider opening: it also accepts coin rolls, envelopes with change or small sealbags. The flap is fitted with an anti-fishing device that makes retrieving the contents more difficult.
In short: for banknotes only, a slot is sufficient; if you also deposit coins or sealbags, a flap is more practical. Please note: both types are not certified, and they offer less protection against fishing out the contents than an EN 1143-2 certified deposit safe such as the Salvus Tivoli or the Robur deposit safes. If the deposited values need to be insured, always choose a certified model.