reprojected coordinates don't match original coordinates

[todddoerr]

I'm using http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer/project to project an esriGeometryEnvelope from GCS_WGS_1984 to USA_Contiguous_Albers_Equal_Area _Conic_USGS_version. Here's my input:

{'geometryType':'esriGeometryEnvelope','geometries':[{'xmin':-127.98775264,'xmax':-118.097294455,'ymin':40.6114817258,'ymax':49.4786153647}]}&f=json&inSR=4326&outSR=102039

This is the output: {u'xmin': -2633438.20097998, u'ymin': 2170059.14546908, u'ymax': 3332882.97158141, u'xmax': -1610306.50465533}

Now I use that output as input to reproject back to GCS_WGS_1984 like this:
{'geometryType':'esriGeometryEnvelope','geometries':[{'xmin':-2633438.20098,'xmax':-1610306.50466,'ymin':2170059.14547,'ymax':3332882.97158}]}&f=json&inSR=102039&outSR=4326

and I get this as my result:
{u'xmin': -132.098826940963, u'ymin': 38.6468804758576, u'ymax': 51.2969623956981, u'xmax': -115.447453297465}

As you can see those final WGS84 coordinates are quite a bit off from my original WGS84 coordinates.  Should they be off by that much?

I've also tried arcpy.Project_management and get the same results.
And I've also tried an intermediate projection (Sphere_Cylindrical_Equal_Area) where my sequence was 4326->53034->102039 and then back 102039->53034->4326 and still get the same results.

Any ideas why this is happening?

Thank you for your help.

Here are the complete to/from REST calls:
http://sampleserver1.arcgisonline.com//arcgis/rest/services/Geometry/GeometryServer/project?geometri...{'geometryType':'esriGeometryEnvelope','geometries':[{'xmin':-127.98775264,'xmax':-118.097294455,'ymin':40.6114817258,'ymax':49.4786153647}]}&f=json&inSR=4326&outSR=102039

http://sampleserver1.arcgisonline.com//arcgis/rest/services/Geometry/GeometryServer/project?geometri...{'geometryType':'esriGeometryEnvelope','geometries':[{'xmin':-2633438.20098,'xmax':-1610306.50466,'ymin':2170059.14547,'ymax':3332882.97158}]}&f=json&inSR=102039&outSR=4326