Ralph Martin has set up a field number data service whereby you can enter a field collector's number for a plant, e.g. "KK 2005", and details of the plant, where it was collected, and other notes will be returned to you.
There is also a related field collector data service whereby you can enter an acronym, e.g. "KK", for a cactus and succulent field collector, and the collector's name and other notes are returned to you. This service knows about more collectors than the field number service; the notes may help you to interpret the results provided by the field number service. The field collector's acronym data service allows you to do the opposite of the above: you can enter the collector's name and the corresponding acronym(s) are returned to you.
There is also a field number finder service where you may enter a species of cactus or succulent e.g. "Rebutia heliosa", and find field numbers corresponding to that species.
Finally, if you want to search for plants found at a given locality e.g. "Sierra Medina", please use the field number locality query service instead.
I am always grateful to receive further data for this service. The best way to prepare your data is in the form of a spreadsheet (Excel or tab-separated text) with one record per line. The columns should be as follows: field number, genus, species, variety (or ssp., fma., etc), locality (place, province, country), altitude, date, notes (any other useful observations, e.g. yellow flowers). The data should be emailed to me at email@example.com.
Any bugs or errors in this service should be reported to me at firstname.lastname@example.org.