As
@mike60smart points out one of the easiest ways to open a form or report to a filter set of records is to do this with the docmd.openForm or docmd.openreport.
Office VBA reference topic
docs.microsoft.com
If your criteria is a string you need to surround with single quotes.
Docmd.openReport
"ReportName", acPreview, , "[Assembly NumberSpec]='" & me.Assembly_NumberSpec & "'"
Also in the future do yourself a big favor and do not put any spaces or special characters in any field names or any other object names. If you have spaces you have to add special handling in all code and queries. The name always has to be in [square brackets]. Not required if no space. In vba the name gets an underscored added automatically.