<entry id="2224294" stat="A" corpus="jmdict" type="jmdict">
<ent_corp type="jmdict">jmdict</ent_corp>
<ent_seq>2648580</ent_seq>
<k_ele>
<keb>芯ケース</keb>
</k_ele>
<r_ele>
<reb>しんケース</reb>
</r_ele>
<sense>
<pos>&n;</pos>
<gloss>pencil lead case (for a mechanical pencil)</gloss>
</sense>
<info>
<audit time="2011-07-20 09:29:16" stat="A" unap="true">
<upd_name>Nils Roland Barth</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_detl>Significantly less common than 芯のケース (with の), but this form is also found.</upd_detl>
</audit>
<audit time="2011-07-21 01:09:19" stat="A">
<upd_uid>jwb</upd_uid>
<upd_name>Jim Breen</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_diff>@@ -12,0 +12,1 @@
+&lt;xref type="see" seq="2648570"&gt;芯のケース・しんのケース&lt;/xref&gt;</upd_diff>
</audit>
<audit time="2023-03-09 07:45:53" stat="A" unap="true">
<upd_name>Brian Krznarich</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_detl>It appears that something reporting numbers back in 2011 was off, because comments are tied together with this and the xref'ed entry.

This seems to be the dominant form(confirming the n-grams, search Amazon and the の form won't appear hardly anywhere on a product listing).

Confirmed by twitter.
People who use の tend no not abbreviate other parts as well, such as...
シャーペンの芯のケース

Interesting

Is this [abbr] if it is the dominant form?    シャー芯ケース , or something even longer, would seem to be the etymological root.</upd_detl>
<upd_refs>芯ケース	1289	67.1%
芯のケース	262	13.6%

シャーペン芯ケース	107	5.6%
シャーペンの芯ケース	102	5.3%
シャーペンの芯のケース	71	3.7%
シャーペン芯のケース	0	0.0%

シャー芯ケース	52	2.7%
シャー芯のケース	37	1.9%
シャーの芯のケース	0	0.0%


Without の (common) 92 hits since march 1
https://twitter.com/search?q=%22%E8%8A%AF%E3%82%B1%E3%83%BC%E3%82%B9%22&amp;src=typed_query&amp;f=live
With の , still present, 12 hits since march 1
https://twitter.com/search?q=%22%E8%8A%AF%E3%81%AE%E3%82%B1%E3%83%BC%E3%82%B9%22&amp;src=typed_query&amp;f=live</upd_refs>
<upd_diff>@@ -12 +12 @@
-&lt;xref type="see" seq="2648570"&gt;芯のケース・しんのケース&lt;/xref&gt;
+&lt;xref type="see" seq="2405790"&gt;シャー芯・シャーしん&lt;/xref&gt;</upd_diff>
</audit>
<audit time="2023-03-10 00:22:43" stat="A">
<upd_uid>jwb</upd_uid>
<upd_name>Jim Breen</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_detl>I don't think that xref is relevant.</upd_detl>
<upd_diff>@@ -12 +11,0 @@
-&lt;xref type="see" seq="2405790"&gt;シャー芯・シャーしん&lt;/xref&gt;</upd_diff>
</audit>
<audit time="2023-03-10 21:26:29" stat="A">
<upd_uid>robin1354</upd_uid>
<upd_name>Robin Scott</upd_name>
<upd_email>...address hidden...</upd_email>
<upd_diff>@@ -12 +12 @@
-&lt;gloss&gt;pencil lead case (for mechanical pencil)&lt;/gloss&gt;
+&lt;gloss&gt;pencil lead case (for a mechanical pencil)&lt;/gloss&gt;</upd_diff>
</audit>
</info>
</entry>