Off-line Quest.

The same search algorithms as for the on-line search have been used to scan the GRBM data archive currently available, covering $\sim$ 80% of all GRBM data. In addition, in the off-line case the search algorithms have been refined, by applying the same criteria with several integration times (1, 2, 4 and 8 s) instead of the only 1 s, as in the on-line case. This refinement has allowed to catch further faint bursts. The on-board trigger efficiency turned out to be $\sim$ 2/3 lower than the off-line quest: in other words, for each two on-board triggered bursts, the off-line search caught a further one missed by the on-board trigger logic. By taking into account the sky exposure, the observed GRB mean rate is $\sim 1.3$ GRB/day, i.e. lower than the BATSE mean rate of 2-3 GRBs/day; this shows that BATSE has a better sensitivity than GRBM. From the analysis of the bursts detected in common with BATSE (both 4B catalog and the two non-triggered burst catalogs by Kommers and by Stern et al.), it has been possible to estimate to GRBM sensitivity as a function of the burst arrival direction with respect to the BeppoSAX local frame of reference; it turns out that the GRBM off-line trigger efficiency, when compared with BATSE, is around 50-60% for all directions, except for the local south pole, where it falls down to 20-30% (in agreement with what expected from the configuration of the GRBM with the satellite, in particular a strong absorption by the electronics box).