Karl,
We use the ADIF standard as a base line for fields and add our own program specific fields where there is no equivalent ADIF field.
Here is a list of the "My......." fields that are currently in the ADIF format
MY_CITY String the logging station's city
MY_CITY_INTL IntlString the logging station's city
MY_CNTY Enumeration function of MY_STATE the logging station's Secondary Administrative Subdivision (e.g. US county, JA Gun) , in the specified format
MY_COUNTRY String Country the logging station's DXCC entity name
MY_COUNTRY_INTL IntlString Country the logging station's DXCC entity name
MY_CQ_ZONE Number the logging station's CQ Zone
MY_DXCC Enumeration Country Code the logging station's Country Code
MY_FISTS String the logging station's FISTS CW Club member information, which starts with a sequence of Digits giving the member's number. For upward-compatibility, any characters after the last digit of the member number sequence must be allowed by applications.
MY_GRIDSQUARE GridSquare the logging station's 2-character, 4-character, 6-character, or 8-character Maidenhead Grid Square
MY_IOTA String the logging station's IOTA designator, in format CC-XXX, where CC is a member of the Continent enumeration XXX is the island designator, where 0 <= XXX ,<= 999 [use leading zeroes]
MY_IOTA_ISLAND_ID String the logging station's IOTA Island Identifier
MY_ITU_ZONE Number the logging station's ITU zone
MY_LAT Location the logging station's latitude
MY_LON Location the logging station's longitude
MY_NAME String the logging operator's name
MY_NAME_INTL IntlString the logging operator's name
MY_POSTAL_CODE String the logging station's postal code
MY_POSTAL_CODE_INTL IntlString the logging station's postal code
MY_RIG String description of the logging station's equipment
MY_RIG_INTL IntlString description of the logging station's equipment
MY_SIG String special interest activity or event
MY_SIG_INTL IntlString special interest activity or event
MY_SIG_INFO String special interest activity or event information
MY_SIG_INFO_INTL IntlString special interest activity or event information
MY_SOTA_REF SOTARef the logging station's International SOTA Reference.
MY_STATE Enumeration function of MY_COUNTRY the code for the logging station's Primary Administrative Subdivision (e.g. US State, JA Island, VE Province)
MY_STREET String the logging station's street
MY_STREET_INTL IntlString the logging station's street
MY_USACA_COUNTIES SecondarySubdivisionList two US counties in the case where the logging station is located on a border between two counties, representing counties that the contacted station may claim for the CQ Magazine USA-CA award program. E.g. MA,Franklin:MA,Hampshire
MY_VUCC_GRIDS - GridSquareList two or four adjacent Maidenhead grid locators, each four characters long, representing the logging station's grid squares that the contacted station may claim for the ARRL VUCC award program. E.g.EN98,FM08,EM97,FM07
The full ADIF specification is available here
http://adif.org/304/ADIF_304.htm