Version of sql server

I have an issue identifying the version of software that was installed on my production server. When I run 

select @@version

I get the following output:
Microsoft SQL Server 2008 R2 (SP1) - 10.50.2500.0 (X64)   Jun 17 2011 00:54:03   Copyright (c) Microsoft Corporation  Standard Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) 

But what I really want to know is was this a direct sqlserver 2008 r2 sp1 install or a sql server 2008 r2 install first and then an upgrade to SP1