The 'Twilight Saga' actor splashed out on a limited edition Bentley fountain pen for his girlfriend to add to her collection and even had the writing tool engraved to commemorate her turning 23 on Tuesday (09.04.13).
A source told the Daily Star newspaper: ''Kristen has always collected pens, and has a variety of stylish ones. Rob decided to go big for her birthday this year and brought her a limited edition white gold Tibaldi Bentley Crewe fountain pen.
''He had her name specially engraved on it with the year and wording: 'From R'.
''There are only 40 of these pens in the world, so it's a real collector's item.''
The 26-year-old actor chose the gift because it had a British history, as it has been created in collaboration between car makers Bentley and Italian luxury pen designers Tibaldi.
The source added: ''The pens have a two-tone 18-carat yellow gold nib covered in rhodium and ruthenium.
''The barrel is identical to Bentley's dashboard used in their earliest car.''
The 'Bel Ami' actor also presented Kristen - who cheated on him last year with married director Rupert Sanders - with an antique bracelet and asked her to officially move back in with him.
The source said: ''They've been taking it slowly, but Kristen has gradually won back his trust.
''Rob has taken a giant leap by officially suggesting they buy a love nest together.''
An onlooker said: ''Rob came in and sat down alone for about five minutes. And then Kristen came in with a security guard and sat down next to Rob. They were all hanging out in front of the other guests and looked like they were having a great time together.''