There were small differences in the appearance of the pens over the years (clip/section/packaging changes) so that would account for different manufacturers being involved in their production --see https://goodwriterspens.com/2011/03/03/the-ty-phoo-tea-pen/
According to the above link, the earliest Ty-Phoo pens were made of BCHR with threaded barrel ends, and then they switched to the mottled red hard rubber that is more familiar to those who know about these pens (there are fewer BCHR examples still around).
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www.newpentrace.net