SQL Join With Unknown Tables - But It Works!?!

Hi all,
While debugging some old code from someone, I came across this stored
procedure:

SELECT dbo.TBL_COORD.COORD_ID AS ID, dbo.TBL_COORD.LATITUDE AS Latitude,
dbo.TBL_COORD.LONGITUDE AS Longitude,
dbo.TBL_COORD.NORTHING AS Northing,
dbo.TBL_COORD.EASTING AS Easting, dbo.refDROP_VALUES.Drop_Value AS [Geometry
Type],
refDROP_VALUES_1.Drop_Value AS [GPS Datum],
refDROP_VALUES_2.Drop_Value AS [GPS Used]
FROM dbo.TBL_COORD INNER JOIN
dbo.refDROP_VALUES ON dbo.TBL_COORD.GEOMETRYTYPE_ID =
dbo.refDROP_VALUES.ID INNER JOIN
dbo.refDROP_VALUES refDROP_VALUES_1 ON
dbo.TBL_COORD.GPS_DATUM = refDROP_VALUES_1.ID INNER JOIN
dbo.refDROP_VALUES refDROP_VALUES_2 ON
dbo.TBL_COORD.GPS_USED = refDROP_VALUES_2.ID
WHERE
<some conditions here>

This query seems to work fine, however I cannot see ANY source to the tables
refDROP_VALUES_1, and refDROP_VALUES_2. There are no views/tables/stored
procedures of any kind with these names in the databse, so I'm at a loss as
to where they're coming from. Note that there IS a table refDROP_VALUES, and
the fields that refDROP_VALUES_1 and refDROP_VALUES_2 reference ARE fields
in the table refDROP_VALUES. I can view the results from running the query.
Whats going on here? Does MS SQL create these tables?

Jack.