I checked today the Item location parameter estimates JAM (R package via SPSS) vs. QUEST using the same large secondary research dataset.
Here are the item location parameter estimates for the first 15 items (please note that several items are grouped around a reading stimulus).
For me, there seems to be a bug in the program as it keeps ignoring items greater than 76 with this dataset and another smaller dataset. It is probably best to explore this issue with the ConQUEST program. (NB: 0,1 item scoring with missing = 9 default).
QUEST also produces location parameter estimates to 2 decimal places. The traditional approach in item response theory is to produce item location parameters to three decimal papers (need to find reference).