Spain Grid UTM_ED_50_ZONE_29_N

[Genrih]

Hello, we have a need in UTM_ED_50_ZONE_29_N Spain grid, but it is absent in GpsTools.

We have created Custom Grid with parameters
Datum ED_50
FalseEasting 500000
Longitude of Origin -9
ScaleFactor 0.9996
(other default)

As mentioned in http://spatialreference.org/ref/epsg/23029/
Input Coordinates: -9, 48.075 Output Coordinates: 500000, 5324740.319972 (Franson CoordTrans gives this results too)
but we receive
E500109.832253411M
N5324858.57194328M

Can you advice something?

[Genrih]

More thoroughly:

Franson CoordTrans
input:
Easting 686643.00 Northing 4115632.00
Grid UTM Zone 29N (European 1950)

output:
WGS84
Longitude 6 deg 53.95343 min
Latitude 37 deg 9.99642 min

Franson GpsTools
input:
Easting 686643.00 Northing 4115632.00
Custom Grid
Algorithm: TRANSVERSE_MERCATOR
Datum: ED_50
FalseEasting: 50000
LongitudeOfOrigin: -9
ScaleFactor: 0.9996
output:
WGS84
Longitude 6 deg 53.94765 min
Latitude 37 deg 9.99735 min

So you can see that GpsTools give different output than CoordTrans. What can be the issue?